TMH Ch. 34 Exercises in Organic Chemistry

Practical organic chemistry:

JEE Syllabus


Detection of elements (N, S, halogens);
Detection and identification of the following functional groups:
hydroxyl (alcoholic and phenolic),
carbonyl (aldehyde and ketone),
carboxyl, amino and nitro;
Chemical methods of separation of mono-functional organic compounds from binary mixtures.


Detection of Elements (N,S, halogens)

Lassaigne test is used for this.

First sodium extract of the given organic compound is prepared.
A pea sized dry piece of sodium metal (freshly cut) is taken in an ignition tube and the tube is heated to melt the sodium metal piece to shining globule. Then a pinch of the organic compound is introduced in the tube. Then the tube is further heated first gently and strongly till the lower end of the tube becomes red hot. The tube is then plunged and broken in about 20 ml. of distilled water taken in porcelain dish. The solution is boiled for about 5 minutes and filtered. The filtrate obtained is known as sodium extract.

Test for Nitrogen

To 2ml of sodium extract, a little ferrous sulphate is added. The solution is boiled and a little dilute sulphuric acid is added. Appearance of prussian blue or green colouration indicates the presence of nitrogen in the compound.

Chapter 13A. Halogens

The Halogens are non-metals and form the 7th Group in the Periodic Table.

'Halogens' means 'salt formers' and the most common compound is sodium chloride which is found from natural evaporation as huge deposits of 'rock salt' or the even more abundant 'sea salt' in the seas and oceans.



Physical properties

• typical non-metals with relatively low melting points and boiling points.
• They are all poor conductors of heat and electricity - typical of non-metals.
• When solid they are brittle and crumbly e.g. iodine.
•
Colour
F Fluorine--- pale yellow gas

Cl Chlorine--- green gas

Br Bromine--- dark red liquid, brown vapour

I Iodine---- dark crumbly solid, purple vapour

At Astatine--- black solid, dark vapour

•
•


important trends down the Group with increasing atomic number
• The melting points and boiling increase steadily down the group (so the change in state at room temperature from gas ==> liquid ==> solid), this is because the weak electrical intermolecular attractive forces increase with increasing size of atom or molecule.
• They are all coloured non-metallic elements and the colour gets darker down the group.
• The size of the atom gets bigger as more inner electron shells are filled going down from one period to another.
Chemical Properties
• The atoms all have 7 outer electrons,
o they form singly charged negative ions e.g. chloride Cl- because they are one electron short of a noble gas electron structure. They gain one negative electron (reduction) to be stable and this gives a surplus electric charge of -1. These ions are called the halide ions, the bromide Br- and iodide I- ions.
o they form ionic compounds with metals e.g. sodium chloride Na+Cl-. (ionic bonding revision page)
o they form covalent compounds with non-metals and with themselves.
o The bonding in the molecule involves single covalent bonds e.g. hydrogen chloride HCl or H-Cl.
• The elements all exist as X2 or X-X, diatomic molecules where X represents the halogen atom.
• A more reactive halogen can displace a less reactive halogen from its salts .
• The reactivity decreases down the group .
• they are all TOXIC elements .
• Astatine is very radioactive, so difficult to study



Reaction with hydrogen H-2

• Halogens readily combine with hydrogen to form the hydrogen halides which are colourless gaseous covalent molecules. e.g. hydrogen + chlorine ==> hydrogen chloride
• H-2(g) + Cl-2(g) ==> 2HCl(g)
• The hydrogen halides dissolve in water to form very strong acids with solutions of pH1 e.g. hydrogen chloride forms hydrochloric acid in water HCl(aq) or H+Cl-(aq) because they are fully ionised in aqueous solution even though the original hydrogen halides were covalent. An acid is a substance that forms H+ ions in water.
• Bromine forms hydrogen bromide gas HBr(g), which dissolved in water forms hydrobromic acid HBr(aq). Iodine forms hydrogen iodide gas HI(g), which dissolved in water forms hydriodic acid HI(aq).

Reaction with Group 1 Alkali Metals Li, Na, K etc.

• Alkali metals burn very exothermically and vigorously when heated in chlorine to form colourless crystalline ionic salts e.g. NaCl or Na+Cl-.
• e.g. sodium + chlorine ==> sodium chloride
• 2Na(s) + Cl2(g) ==> 2NaCl(s)
• The sodium chloride is soluble in water to give a neutral solution pH 7, universal indicator is green. The salt is a typical ionic compound i.e. a brittle solid with a high melting point. Similarly potassium and bromine form potassium bromide KBr, or lithium and iodine form lithium iodide LiI.
•
Reaction with other metals
• If aluminium or iron is heated strongly in a stream of chlorine (or plunge the hot metal into a gas jar of chlorine carefully in a fume cupboard) the solid chloride is formed.
• aluminium + chlorine ==> aluminium chloride(white):
o 2Al(s) + 3Cl2(g) ==> 2AlCl3(s)
• iron + chlorine ==> iron(III) chloride(brown):
o 2Fe(s) + 3Cl2(g) ==> 2FeCl3(s)
• If the iron is repeated with bromine the reaction is less vigorous, with iodine there is little reaction, these also illustrate the halogen reactivity series.

Study Guide TMH Chemistry 34. Exercises in Organic Chemistry

-----------------
JEE question 2007 Paper II

Riemer-Tiemann reaction introduces an aldehyde group, on to the aromatic ring of phenol, ortho to the hydroxyl group. This reaction involves electrophilic aromatic substitution. This is a general method for the synthesis of substituted salicylaldehydes.

1. Which one of the following reagents is used in the above reaction?
(A) aq.NaOH+ CH-3Cl
(B) aq.NaOH+ CH-2Cl-2
(C) aq.NaOH+ CHCl-3
(D) aq.NaOH+ CCl-4


Answer C

Reimen-Tiemann reaction takes place is presence of aq. NaOH+ CHCl3

2. The electrophile in this
(A) :CHCl
(B) +CHCl-2
(C) :CCl-2
(D) :CCl-3

Answer: C
-------------------------------

Study Guide TMH JEE Ch.28 Carboxylic Acid

JEE syllabus

Carboxylic acids:
Preparation, properties
Characteristic reactions
formation of esters,
acid chlorides and amides,
ester hydrolysis;

----------
Main Topics Covered in the TMH Book

METHODS OF PREPARATION
PHYSICAL PROPERTIES
CHEMICAL REACTIONS
FUNCTIONAL DERIVATIVES OF CARBOXYLIC ACIDS

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Carboxylic acids are the compound containing carboxyl group in their molecules.

-c with a double bond with oxygen and single bond with OH


The carboxyl group is made up of carbonyl C with double bond with oxygen, and hydroxyl group OH. The carboxyl is formed carbo + oxyl.

These acides can be aliphatic or aromatic.

aliphatic acids

Formic acid HCOOH
Acetic acid CH-3COOH
Isobutyric acid (Branched)

aromatic acids

Bezoic acid : H in benzene substituted by COOH

m-Nitrobenzoic acid: One more H substituted by NO-2

o-Toluic acid (o refers to ortho) Benzoic acid with one more H substituted by CH-3

Dicarboxyic acids

Oxalic acid
Malonic acid
Succinic acid
Phthalic acid - It is an aromatic carboxylic acid

In the nomenclature, in common system, position of the sustituents is indicated by the greek letter alpha, beta, gamma and delta.

the carbon atom adjacent ot the carboxyl carbon is assigned the letter α, thenext carbon on chain is beta an so on.

According to the IUPAC system, the name of the acid is derived from the corresponding alkane by replacing the terminal 'e' with the '-oic' and adding the word acid.

The position of the substituents is indicated by the following rules:
1. The longest chain containing the carboxylic group (-COOH) is selected.
2. The carbon chain is numbered form the carboxylic acid group. The carbon of carboxyl group is always given number one.
3. The position of the substituents is indicated by the number.

Methods of Preparation of Monocarboxylic Acids:
1. From oxidation of primary alcohols
2. By oxidation of aldehydes and ketones.
3. By Hydrolysis of cyanides (or Nitriles)
4. By Grignard reaction
5. By hydrolysis of esters
6. By carboxylation of alkenes
7. From trihalogen derivatives of hydrocarbons
8. Aromatic acids from alkyl benzenes

Physical properties

State
B.P.
M.P.
Solubility


Reactions of carboxylic Acids

covered under the following heads

A. reactions due to hydrogen atom of carboxyl group
B. reactions due to OH carboxyl group
C. reactions due to carboxyl group
D. reactions due to alkyl group and benzene ring.


A. reactions due to hydrogen atom of carboxyl group

1. Acidic Properties

B. reactions due to OH carboxyl group
1. Formation of an acid anhydride
2. Formation of Esters (specially mentined in JEE syllabus)
3. Formation of amides (specially mentined in JEE syllabus)
4. Formation of acid chlorides (specially mentined in JEE syllabus)

C. reactions due to carboxyl group
1. Decarboxylation
2. Reduction
3. Action of bromine on silver salt of the acid
D. reactions due to alkyl group and benzene ring.
1. Halogenation
2. Ring substitution in aromatic acids

Ester hydrolysis (specially mentined in JEE syllabus) (from jauhar's book section on esters page 806)
---------
web sites
www.goiit.com/chapters/tutorial/chemistry/carboxyllic_acid.htm

TMH JEE Book Chapters

Physical Chemistry

1. The Concept of Atoms and Molecules
2. Gaseous, Liquid and Solid States
3. Atomic Structure
4. Periodicity of Properties of Elements
5. Bonding and Molecular Structure
6. Energetics
7. Chemical Equilibrium
8. Electrochemistry
9. Solutions
10. Chemical Kinetics
11. Surface Chemistry
12. Nucluear Chemistry

Inorganic Chemistry
13. Non-Metals
14 Compounds of Metals
15 Compound of Nonmetals
16 Transition Elements
17 Ores/Minerals and Extractive Metallurgy
18. Exercises in Inorganic Chemistry

Organic Chemistry

19. Hybridization, Isomerism
20. Inductive and Resonance Effects
21. Alkanes
22. Alkenes
23. Alkynes
24. Benzene
25. Alcohols
26. Alkyl and Aryl Halides
27. Aldehydes and Ketones
28. Carboxylic Acids
29. Phenols
30. Amines
31. Carbohydrates
32. Aminoacids and Peptides
33. Polymers
34. Exercises in Organic Chemistry

TMH-JEE-chemistry-Study Guide - ch 23 Alkynes Part 2

Chemical Properties

The alkynes have at least one triple bond in them, therefore, they are quite reactive chemically.

They readily take part in addition reactions and can also be easily oxidized.

I. Addition reactions (specially given in jee syllabus)

1. Addition of Hydrogen

If the triple bond is not present at the end of the chain of the molecule (it is not a terminal alkyne), its reduction (addition of hydrogen) produces either a cis alkene or a trans alkene depending upon the choice of reducing agent.

2. Addition of halogens

chlorine and bromine add on alkali

3. Addition of hydrogen halides

This addition takes place in accordance with Markonikov's rule(do you remember the rule?).
Peroxides have the same effect on addition of the HBr to acetylenes (alkynes) as they have on alkenes (do you remember the effect?).

4. Addition of water (hydration of alkynes) (specially given in jee syllabus)
In the presence of acid (H2SO4) and HgSO-4, a molecule of water adds to the triple bond at 348K. The catalyst in this reaction is HgSO4 (Mercuric sulphate). The final products of this reaction are carbonyl compounds aldehydes and ketones.

Initially enol is formed which is raidly converted into an equilibrium mixture containing keto form in excess. Enol is so called because it contains 'ene' (double bond) and an alcoholic group (ol).

Examples:
Addition of water to Ethyne or acytelene: Acetylene is passed into water (at about 330K) containing 60% H2SO4 and about 1% mercuric sulphate (HgSO4) as a catalyst, acetaldehyde is formed.

In the first step 'ethenol' is formed and in the second step the rearrangement of it takes place and its isomer 'acetaldehyde' is formed.

The conversion of enol form into keto form is termed tautomerism



5. Addition of hypohalous acid (HOX)

Alkynes react with two molecules of hypohalous acids in two stages.
For example take ethyne or acytelene and HOCl.
In the first stage HO gets added to one carbon and Cl adds to the other carbon.
In the second stage one more HOCl gets added to the intermediate product which has a double bond. The addition now follows markonikov's rule. OH gets added to HC-OH and Cl gets added to CH-Cl. Two OHs create instability and H2O molecule gets removed.
An aldehyde 2,2-Dichloroethanal (Dichloroacetaldehyde) is formed.

6. Addition of H2SO4 (Ref: Standard XI Chemistry by Khan et al, Uttam Prakashan)
Acetylene adds two molecules of concentrated H2SO4 in two stages and forms ethylidene hydrogen sulphate as the final product.

In the first stage Vinylhydrogen sulphate H2C=CH-OSO3H is formed. (H gets added to one CH and OSO3H gets added to the other CH).
The addition of second molecule follows markownikov's rule. H gets added to CH2 and OSO3 gets added to the other carbon. Thus two functional groups OSO3H gets added to one carbon.
The final product is Ethylidine hydrogen sulphate.


II. Oxidation

a) Combustion

b) Oxidation with alkaline potassium permanganate

c) Ozonolysis

Alkynes react with ozone to form ozonides. These ozonides on decomposition with water in the presence of zinc give diketones(two carbonyl groups).

Ethyne gives glyoxal on reacting with ozone. Glyoxal also have two carbonyl groups.

III. Polymerization

a) Acytylene dimerizes (two molecules come together as one molecule) in the presence of cuprous chloride and ammonium chloride to give vinyl acetylene which on reacting with HCl gives chloroprene.

The later polymerizes to give neoprene - a synthetic rubber.

b) Cyclic polymerization

This takes place when alkyne is passed through red hot iron tube at 400 degress celsius.

Occurs in two stages. Acetylene becomes mesitylene.

IV. Isomerization

1-alkyne gets converted to 2-alkyne and vice versa.

V. Formation of metal acetylides (specially given in jee syllabus)

Acytelene reacts with Na and LI liberating H-2 gas and forming metal acetylide. Therefore acetylene has chemical behaviour similar to acids.

Heavy metal ions mainly, Ag+ and Cu+ react with acetylinic hydrogen (hydrogen atom in acetylene) to form insoluble acetylides.

VI. Reaction with Grignard reagent or alkyl-lithium

The acytylinic hydrogen on reacting with R'MgBr or R'Li produces the alkane R'H and metal acetylide



Acidic property of acetylene (specially given in jee syllabus)

Acetylene and other terminal alkynes (1-alkynes) are weakly acidic in character.
They react with strong bases like NaNH2 ( sodium in liquid ammonia) to form sodium acetylide derivatives known as acetylides or alkynides.

Acetylides react with alkyl halides to give higher alkynes.

Explanation for the acidic character of alkynes

the acidic character of 1-alkynes can be explained on the basis of sp hybridisation state of the carbon atoms in alkynes. In sp hybridisation, s-character is 50% and due to this large s-character, the electons in sp hybrid orbitals are held more tightly by thenucleus and areq uite electronegative. Consequently the eletron pair of H-C≡C bond gets displaced more towards the carbon atom and helps in release of H+ ion.

In the case of nonterminal alkynes, hydrogen atom is not attached directly to the triple bonded carbon atom and hence it is not released easily.

Alkynes are weakly acidic but alkenes and alkanes do not show acidic behaviour.

acidic charater
HC≡HC > CH2=CH2 > CH3-CH3

The relative acidity of acetylene is more than that of ammonia but less than that of water.

Dissolving Metal Reduction of Alkynes (specially given in jee syllabus)

Reaction Type: Addition

Summary

Alkynes can be reduced to trans-alkenes using Na in NH3 (l)
This reaction is stereospecific giving only the trans-alkene via an anti addition.
Note that the stereochemistry of this reaction complements that of catalytic hydrogenation (syn)
The reaction proceeds via single electron transfer from the Na with H coming from the NH3
These reaction conditions do not reduce alkenes, hence the product is the alkene.

MECHANISM FOR THE REDUCTION OF ALKYNES WITH Na / NH3
Step 1:
Sodium transfers an electron to the alkyne giving a radical anion.
Step 2:
The radical anion removes a proton from the ammonia in an acid / base reaction.
Step 3:
A second atom of sodium transfers another electron to the alkyne giving an anion.
Step 4:
The anion removes a proton from the ammonia in an acid / base reaction.
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Source for reduction
http://library.tedankara.k12.tr/carey/ch9-7.html
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Study Guide TMH JEE Ch.23 Alkynes

JEE syllabus

Preparation, properties and reactions of alkynes:

Physical properties of alkynes (boiling points, density and dipole moments);
Acidity of alkynes;
Acid catalysed hydration of alkynes (excluding the stereochemistry of addition and elimination);

Reduction of alkynes;
Preparation of alkynes by elimination reactions;
Addition reactions of alkynes;
Metal acetylides.
----------------------

Main Topics Covered in the TMH Book

METHODS OF PREPARATION
CHEMICAL PROPERTIES

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From X class book

General formula: C(n)H(2n-2)
================================================
Structural--------------Common------------IUPAC
Formula:----------------name--------------name
------------------------------------------------
C two H two ---------Acetylene------------------Ethyne
C three H four------ Methyl acetylene-----------Propyne
C four H six *------ ethyl acetylene------------1-Butyne
--------------------------------------(Triple bond is the
--------------------------------------first carbon bond)
C four H six*--------Dimethyl acetylene---2-Butyne
---------------------------------------(Triple bond is the
----------------------------------------2nd carbon bond)
=========================================================


Preparation of Ethyne:

1. Calcium Carbide + Water = Ethyne + Calcium Hydroxide

(Cold water is added dropwise through a thistle funnel into conical flask containing calcium carbide at room temperature)

2. By dehydrohalogenation reaction

1,2 dibromoethane + KOH(alcoholic) = Ethyne + KBR + water (equation not balanced)

3. Methane on thermal decomposition by pyrolysis gives Ethyne + Hydrogen at around 1500 degree Celsius in an electric arc.
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Methods of Preparation of Alkynes; From TMH Book

1. Dehydrohalogenation of vicinal dihalides (came in X class book).

What are vicinal dihalides?

term used to describe the location of two identical chemical groups or atoms which are bonded to adjacent carbon atoms.

The process takes place in two stages.

In stage I KOH(alc) reacts with vicinal dihalide and vinylic halide is formed.

what is vinylic halide?

A vinyl halide in chemistry is any alkene with at least one halide substituent bonded directly on one of the unsaturated carbons.

This first stage requires mild conditions.

second stage: Vinyl halide is unreactive and hence vigorous conditions are required and a strong base NaNH two is used in the reaction to produce the corresponding alkyne.

2. Reaction of metal acetalides with primary alkyl halides. This method can be used to generate large alkyne from the smaller one.

Secondary and tertiary halides cannot be used because eliminatin is the predominant reaction which results in the formation of alkenes.

3. Hydrolysis of CaC two and Mg two C three.

Calcium carbide in reaction with water gives ethyne and calcium hydroxide.(came in X class)
Magnesium carbide in reaction water gives propyne and magnesium hydroxide.

4. Kolbe's Electrolytic Method:
The electrolysis of an acqueous solution of potassium salt of an unsaturated dicarboxylic acid forms alkyne



what is a dicarboxylic acid?


Dicarboxylic acids are organic compounds that are substituted with two carboxylic acid functional groups. In molecular formulae for dicarboxylic acids, these groups are often written as HOOC-R-COOH, where R is usually an alkyl, alkenyl, or akynyl group. Dicarboxylic acids can be used to prepare copolymers such as nylon and polyethylene terephthalate.

In general, dicarboxylic acids show the same chemical behaviour and reactivity as monocarboxylic acids. The ionization of the second carboxyl group occurs less readily than the first one. This is because more energy is required to separate a positive hydrogen ion from the doubly charged anion than from the single charged anion.

A mnemonic to aid in remembering the order of the common nomenclature for the first six dicarboxylic acids is "Oh my, such great apple pie!" (oxalic, malonic, succinic, glutaric, adipic, pimelic).

When one of the carboxy groups is replaced with an aldehyde group, the resulting structure is called a "aldehydic acid".


5. Dehalogenation of vic-tetrahalogen compounds

Tetrahalogenated alkane in reaction with zinc with ethyl alcohol as catalyst gives alkyne and zinc halide.
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From the Book by Madan and Bisht: preparation of Acetylene or Ethyne

1. By the action of Alcoholic Potash on Ethylene Bromide

BrH two C - CH two Br + 2KOH = C Two H Two + @KBr + 2 H two O

At the end of first state vinyl bromide is formed.

2. By heating tetra-bromoethane with Zinc

C-two H-two Br-four +2Zn = C-two H-two + 2ZnBr-two

3. By the electrolysis of Acqueous solution of Potassium salts of maleic acid (Kolbe's method)

4. By the action of water on calcium carbide (already covered earlier)

5. By heating Iodoform with silver powder

2HCI-three + 6Ag = C-twoH-two + 6AgI

6. By partial oxidation of Methane

2CH-four + 3[O] = C-twoHtwo + 3H-two O

7. By direct synthesis of carbon and hydrogen (Berthelot's synthesis)

2C + H-two = C-twoH-two

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From Jauhar's book

1. Action of water on calcium carbide
2. Dehydrohalogenation of vicinal dihalides
3. Action of zinc on tetrahalogen derivatives of alkanes
4. From acetylene
5. By electrolysis of aqueous solution of potassium salt of fumaric acid
6. Synthesis of carbon and hydrogen

Industrial preparation
Ethyne is prepared on an industrial scale by treating calcium carbide with water.
-------------------------
Physical properties

State; first three members are gases at room temperature. thenext eight are liquids while the higher ones are solids.

Solubulity: are mostly insoluble in water nbut are soluble in organic solvents such as petroleum, ether, carbon tetrachlorde. benzene etc.

M.P. and B.P.

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Simple questions on methods of preparing alkynes are given in practice questions for review of concepts of this topic.
http://iit-jee-chemistry-ps.blogspot.com/
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TMH-JEE-Chemistry- book-chapters Ch.30 Amines Study Guide/Note

JEE syllabus:

JEE Syllabus

Amines:
Preparation, Properties, Reactions
Charcteristic reactions
Basicity of substituted anilines and aliphatic amines,
Preparation from nitro compounds,
Reaction with nitrous acid,
Azo coupling reaction of diazonium salts of aromatic amines,
Sandmeyer and related reactions of diazonium salts;
Carbylamine reaction;
------------------

Main Topics Covered in the TMH Book

METHODS OF PREPARATION
PHYSICAL PROPERTIES
CHEMICAL REACTIONS
SYNTHETIC USE OF DIAZONIUM SALT
SEPARATION OF A MIXTURE OF AMINES

---------------------------
Amines are regarded as derivatives of ammonia in which one, two or all three hydrogen atoms are replaced by alkyl or aryl group.

NH3 - H = RNH2; (Primary amine) characteritic group NH2 amino
RNH2 - H = R2NH;(secondary amine) characteritic group NH imino
R2NH - H = R3N (tertiary amine) characteritic group N tert-nitrogen

The amines are classified as primary, secondary and tertiary according to one, two or three hydrogen atoms of ammonia are replaced by alkyl or aryl groups.

In addition, there is another class known as quaternary ammonium compounds. These compounds are regarded as derivatives of ammonium salts in which all the four hydrogen atoms are replaced by alkyl or aryl groups.

Nomenclature of amines

IUPAC NAMES

Aliphatic amines

Methanamine
Ethanamine
1-Propanamine
2-Propanamines
N-methylmethanamine
N-Methylethanamine
N,N-Dimethylmethanamine

Aromatic amines

Benzenamine - can also be written as amino benzene
2-Methylbenzenamine
3-Methylbenzenamine
4-Methylbenzenamine
N-Methylbenzenamine
N,N-Dieethylbenzenamine


Isomerism in amines

1. Chain isomerism
2. Metamerism
3. Position isomerism
4. functional isomerism

Preparation of amines

1. From alkyl halides
2. From Nitro compounds (specially mentioned in JEE syllabus)
3.From nitriles (cyanides) and isonitriles (isocyanides)
4. From amides
5. From oximes
6. from aldehydes and ketones

Industrial preparation
1. from alcohols
2.from aniline

Physical properties

1. State and smell
2. B.P.


Chemical Properties
1. Reaction with water (Basic character of amines) (specially mentioned in JEE syllabus)
2. Reaction with acids
3. Reaction with metal ions
4. Alkylation
5. Acylation (reaction with acid chlorides and acid anhydrides)
6. Benzoylation
7. schiff's base formation
8. Oxidation
9. Carbalamine reaction (specially mentioned in JEE syllabus)
10. Reaction with nitrous acid (specially mentioned in JEE syllabus)
11. Reaction with Grignard reagent
12. Carbon disulphide
13. Carbonyl chloride
14. Ring substitution in aromatic amines
15. coupling of diazonium salts (specially mentioned in JEE syllabus)
Sandmeyer and related reactions (specially mentioned in JEE syllabus)
The diazonium salts have the general formula ArN2+X-, where X- may be an anion like Cl-, Br- etc.

The group N2+ (-N≡N+) is called diazonium ion group.

Sandmeyer reaction is a substitution reaction.

In the substistution reactions, nitrogen of the salts is lost as N2 and different groups are introduced in its place.

Various substitution reactions of diazonium salts

1. Replacement by -OH group. By boiling or by steam boiling. Phenol is formed

2. Replacement by hydrogen. By treatment with hypophophorous acid. Benzene is obtained.

3. Replacement by Cl and Br group.When the salt is warmed with cuprous chloride or cuprous bromide the corresponding halide is formed. This reaction is called Sandmeyer reaction
-------------
Past JEE Questions

How will you convert 4-nitroaniline to 1,2,3-tribromobenzene? 1990

1991
Identify A, B and c in the following reactions

C6H5COOH + PCl5--->A
A + NH3---> B
B+ P2O5---->C6H5CN
C6H5CN +(H2, Ni)--->C

Some of the reactants can be catalysts.

1994
How will you synthesize benzamide from nitrobenzene.

1997

How will you prepare m-bromoiodo benzene from benzene?

1998
Write the structures of two products of the reaction.

CH3CONHC6H5 (Br2,Fe) ---->

1998

Arrange the following in the decreasing order of basic character

Methylamine, dimethylamine, aniline, N-methylaniline


2000
How would you bring about conversion of Aniline to Benzylamine.

2001

Aspartame an artificial sweetener, is a peptide and has the following structure.
(Structure not given here by me)
i) Identify the four functional groups.
ii) Write the zwitter ionic structure
iii) Write the structures of the amino acids obtained from the hydrolysis of aspartame.
iv) Which of the two amino acids is more hydrophobic?


-----------------
web sites
Notes on the Classification, Structure and Nomenclature-naming of Organic compounds containing Nitrogen
http://www.docbrown.info/page07/orgNcmpds.htm

TMH-JEE-Chemistry- book-chapters Ch.31 Carbohydrates Study Guide/Note

JEE Syllabus

Carbohydrates:
Classification;
mono and di-saccharides (glucose and sucrose);
Oxidation, reduction,
glycoside formation and hydrolysis of sucrose.
--------------
Main Topics Covered in the TMH Book

MONOSACCHARIDES
DISACCHARIDES
POLYSACCHARIDES
-------------






Carbohydrates means "hydrates of carbon".
These are poly-hydroxylated-aldehydes or poly-hydroxylated-ketones. The general formula is C-x(H-2O)-y

Aldehydes are compounds containing the carbonyl group -C=O as functional groupThe general formula is C-nH-2n-O, In aldehydes, the carbonyl carbon atom carries at least one H e.g.,

H
!
C=O
!
H

Formaldehyde


CH-3
!
C=O
!
H

Acetaldehyde

Ketones also have the same general formula C-nH-2nO but, the carbonyl atom does not carry any H atoms, but it is attached to two alkyl or aryl groups

CH-3
!
C=O
!
CH-3
It is Dimethyl ketone or Acetone. Its IUPAC name is Propanone




Carbohydrates are classified as:
Monosaccharides

Oligosaccharides

Polysaccharides

Monohydrates may be represented as follows
H
!
C=O
!
(H-C-OH)-n
!
CH-2OH

A polyhdroxy aldehyde

CH-2OH
!
C=O
!
(H-C-OH)-n
!
CH-2OH

A polyhdroxy ketone

Monosaccharides are named as follows.
1. The calss name of monosaccharides begins with the prefix 'aldo' for polyhydroxy aldehydes and "keto' for polyhydroxy ketones.
2. the name ends with suffix 'ose".
3. In between prefix and suffix, the number of carbon atoms (i.e. di, tri, tetr etc.) is inserted.

Examples

H
!
C=O
!
(H-C-OH)
!
CH-2OH

Aldotriose - (A polyhdroxy aldehyde)

CH-2OH
!
C=O
!
CH-2OH

Ketotriose - (A polyhdroxy ketone )

Reducing and Nonreducing Sugars

Reducing sugars are easily oxidized to give carboxylic acid.

They reduce
(i) Tollens reagent (an ammoniacal solution of silver nitrate) to shiny silver mirror.
(ii) Fehling's solution (an acqueous solution of cupric iron and tartrate salts) to red precipitate of cuprous oxide, and
(iii) Benedict's reagent (an alkaline solution containing a cupric citrate complex) to red precipitate of curous oxide)

---------------------------------------------
JEE Question 2007 Paper II

STATEMENT.1: Glucose gives a reddish brown precipitate with Fehling’s solution.

Because

STATEMENT.2: Reaction of glucose with Fehling’s solution gives CuO and gluconic acid.


(A) Statement.1 is True, Statement.2 is True; Statement.2 is a correct explanation for Statement.1.
(B) Statement.1 is True, Statement.2 is True; Statement.2 is NOT a correct explanation for Statement.1.
(C) Statement.1 is True, Statement.2 is False.
(D) Statement.1 is False, Statement.2 is True.

Answer: C.

Cu-2O is given not CuO.
--------------------------
Statement 1 is True. But statement 2 is false because Cu-2O Cuprous oxide is formed and not CuO.
---------------------------------------------

All aldoses are reducing sugars, but some ketoses are reducing sufars as well. For example, fructose (a ketose) reduces Tollens reagent. This occurs because fructose is readily isomerized to an aldose in basic solution.









A set of questions on this chapter posted in

www.iit-jee-chemistry-ps.blogspot.com

TMH-JEE-book-chapters Ch.32 Amino Acids

JEE Syllabus

Amino acids and peptides:
General structure (only primary structure for peptides) and
physical properties.
-----------------
Main Topics Covered in the TMH Book

AMINO ACIDS
PEPTIDE LINKAGE
---------------

amino acids are organic compounds containing both an amino group (NH2) and carboxylic group (COOH). They are represented by the general formula:
R
|
C-COOH
|
NH2


Essential amino acids

These amino acids are required by the body but are not made by our bodies. hence they must be supplied in diets.

Valine
Leucine
Isoleucine
Phenylalanine
Methionine
Trptophan
threonine
Lysine
Agrinine


L-Family of Amino Acids
With the exception of glycine, all other α amino acids have chiral carbon atom and have two optically active isomers.

However all naturally occurring amino acids belong to L series which have -NH2 group on the left.



Structure of Amino acids

amino acids exist as dipolar ion called a zwitter ion.

i) when an acid is added to an amino acid-COO- accepts this proton and therefore the basic character is due to -COO-group.

ii) When an alkali is added to amino acid -NH3+ group releases the proton and therefore acidic character is due to -NH3+ group.

Peptide

peptides are compounds formed by the condensation of two or more same or different α amino acids. The condensation occurs between amino acids with the elimination of water. In this case,the carboxyl group of one amino acid and amine group of another amino acid gets condensed with the elimination of water molecule. The resulting C-N linkage is called peptide linkage. The bond of C with O becomes a double bond.

The formation of peptide can be between two amino acid molecules or the number can go on until a single molecule containing several hundred thousands of aminoacids is formed.


Proteins

Structurally, proteins are long polymers of amino acids linked by peptide bonds




There is a question is about optical activity of amino acids in TMH JEE book. Which amino acid does not exhibity optical activity?

I did a google search on optical activity of organic chemical compounds and I got the following entries.

http://en.wikibooks.org/wiki/Organic_Chemistry/Chirality/Optical_activity



http://www.chemguide.co.uk/organicprops/aminoacids/background.html



Optical activity

If you look yet again at the general formula for an amino acid, you will see that (apart from glycine, 2-aminoethanoic acid) the carbon at the centre of the structure has four different groups attached. In glycine, the "R" group is another hydrogen atom.


This is equally true if you draw the structure of the zwitterion instead of this simpler structure.

Because of these four different groups attached to the same carbon atom, amino acids (apart from glycine) are chiral.


Hence the amino acid Glycine does not exhibit optical acivity. This is the answer to the question.
------------------

A set of questions for practice on this chapter posted in

www.iit-jee-chemistry-ps.blogspot.com

TMH JEE Org. Chemistry CH 33 Polymers

JEE syllabus

Properties and uses of some important polymers:
Natural rubber,
cellulose,
nylon,
teflon and
PVC.
-----------------

Main Topics Covered in the TMH Book

POLYMERS
SOME EXAMPLES OF STEP-GROWTH POLYMERS
---------------

A polymer is a large molecule built by repetitive binding together of many small units called monomers.

Homopolymer: A polymer derived from a single repeating monomer. Only one type of monomer will have repetitive binding and a large molecule appears.

Copolymer: When two or more different monomers bind together in a repetitive manner and give rise to a large polymer, it is called copolymer.

Classification of Polymers

Classification based on source:

Natural and synthetic

Classification based on structure:

1.Linear polymers
2. Branched chain polymers
3. Cross linked polymers

Classification based on molecular forces and physical properties

1. Elastomers
2. Fibres
3. Thermoplastics
4. Thermosetting polymers

Classification based on mode of synthesis:

1. addition polymers
2. Condensation polymers

Methods of Polymerisation

Synthetic polymerisation processes are categorised as Chain growth and step growth polymerisation.

Chain growth polymerisation: Also called addition polymerisation.

In this process, the combination of monomers does not result in elimination of some by product molecules. The process is initiated by by a free radical, a cation or an anion and once initiated, the process gets repeated as a chain reaction as the process produces bigger and bigger active molecules.

Illustrative Model
1. Initiator --> I* a reactive species
2. I* + M (monomer) --> IM* (bigger reactive species)
3. IM* + M --> IMM*
4. IMM* + M --> IMMM*

The chain stops when the active end reacts with a species giving a molecule without the reactive end.

Many vinyl polymers (Vinyl indicates compounds having double bonds) are formed by chain growth polymerisation (chain reaction polymerisation).

Step Growth polymerisation: Also called as condensation polymerisation

In condensation polymerisation, two or more different monomers combine together and in this process of combination elimination of simple molecules like water, ammonia, hydrogen chloride etc. takes place. So there is a condensation in this process of polymerisation.

In this polymerisation generally the monomers contain two functional monomers (difunctional monomers). In this process, the polymerisation takes place step by step.

Illustratitive model

A + B --> A-B
A-B + A --> A-B-A
A-B-A + B --> A-B-A-B

It can also be
A-B + A-B --> A-B-A-B






Properties and uses Natural rubber

Rubber is a naturally occuring polymer. It is obtained as latex from rubber trees. It is highly elastic.

It is a polymer of isoprene (2-methyl buta-1,3-diene)

In natural rubber, about 11,000 to 20,000 isoprene units are linked together in a chain like arrangement.

Natural rubber is a thermoplastic. It becomes soft and sticky when heated. It is not hard and tough.t The properties can be modified and improved by the process of vulcanization.

Properties and uses cellulose



Properties and uses nylon

The monomer of nylon 6 is caprolactum.
fabrics, ropes and tyre cords are prepared using nylon 6.

For nylon 66, the monomers are hexamethylenediamine and adipic acid.
Bristles for brushes, and textile sheets are made using nylon 66

Properties and uses teflon

It is an addition polymer of tetrafluoroethylene.

nF2C=CF2 under heat and pressure (-F2C-CF2-)n
The double bond breaks and gets ready for bonding with a carbon on either side and the polymerisation takes place.

It is a tough material and is resistant towards heat, action of chemicals such as acids and bases. It is bad conductor of electricity.


Properties and uses PVC.
PVC is polyvinyl chloride
Its monomer is vinyl chloride. CH2=CHCl
PVC is prepared by heating vinyl chloride in an inert solvent in the presence of peroxides ( for instance, dibenboyl peroxide)

The double bond breaks and becomes ready bonding to carbon on either side and polymerisation takes place.

PVC is hard horny material. It is a thermoplastic polymer andits plasticity can be increased by the addition of plasticizer usch n-butylphthalate.

PVC is used in the manufacture of rain coats, hand bags, curtain clothes,and toys.
It is also used in articial flooring, as an insulating material in electric wires and for making gramophone records.


----------------------------------

A set of questions on this chapter posted in

www.iit-jee-chemistry-ps.blogspot.com

TMH JEE Chemistry Chapters - List

Organic Chemistry chapter names TMH IIT JEE Chemistry
19. Hybridization, Isomerism
20. Inductive and Resonance Effects
21. Alkanes
22. Alkenes
23. Alkynes
24. Benzene
25. Alcohols
26. Alkyl and Aryl Halides
27. Aldehydes and Ketones
28. Carboxylic Acids
29. Phenols
30. Amines
31. Carbohydrates
32. Aminoacids and Peptides
33. Polymers
34. Exercises in Organic Chemistry