Sunday, September 28, 2008

Tautomerism and Enols - July Dec Revision

Tautomerism

Tautomerism may be defined as the phenomenon in which a single compound exists in two readily interconvertible structures that differ markedly in the relative position of at least one atomic nucleus, generally hydrogen. The two different structures are known as tautomers of each other.

In the presence of acid or base, ketone or aldehyde with α-hydrogen is converted into hydroxyl ene (called enol), hence this type of isomerism in which keto and enol forms exist in dynamic equilibrium is also called ket-enol isomerism.


Enols

Preparation of aldehydes and ketones from alkynes

Hydration of alkynes in the presence of dilute sulphuric acid and HgSO4 as catalyst gives aldehydes and ketones.

Water adds to alkynes to form unstable enol intermediates which rearrange to form aldehydes or ketones.

Hydration of acetylene gives acetaldehyde.

Hydration of alkynes other than acetylene gives ketones.




Addition of water to alkynes (hydration of alkynes)

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).



IIT JEE Revision - Acid Catalysed Hydration of Alkynes
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).

Example:
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

Saturday, September 20, 2008

JEE 2009 Notification

IIT Joint Entrance Examination (JEE 2009) Schedule
April 12, 2009 (Sunday)
09.00 –12.00 hrs Paper – 1
14.00 - 17.00 hrs Paper - 2

Paper – 1 and Paper – 2 will each have three separate sections on Physics, Chemistry, Mathematics. Both the papers will be objective types, designed to test comprehension, reasoning and analytical ability of candidates.

* Eligibility requirements for this examination and syllabus for Physics, Chemistry, Mathematics and Aptitude Test will be available on the websites of all IITs and will also be given in the Information Brochure of JEE – 2009.
*Candidates will have the option of submitting either on – line through internet) or paper application form- offline.
* Important dates regarding Application Form and Brochure:

Sale at designated branches of Banks and at all IITs: Nov 19 - Dec 24 2008
Postal Request of Application form: Nov 19 - Dec 16 2008
Last date of receipt of completed application forms at IITs : Dec 24 2008

Monday, September 15, 2008

Morrison and Boyd Organic Chemistry

Download Link

http://www.4shared.com/file/32409442/231895d7/Morrison__Boyd--Organic_chemistry.html?s=1

Morrison and Boyd - Organic Chemistry - Slides - Notes II

Topics covered

Infrared Spectroscopy

Nuclear Magnetic Resonance

Spectrocopy Tables (IR & nmr)

Aldehydes & Ketones I

Aldehydes & Ketones II

Carboxylic Acids

Functional Derivatives of Carboxylic Acids

Carbanions I

Carbanions II

a,b-Unsaturated Carbonyls

notes on exam II

Amines, Syntheses

Amines, Reactions

Diazonium Salts

Phenols

Aryl Halides

Molecular Orbitals and Conservation of Symmetry

Polynuclear Aromatics

Heterocyclics

Carbohydrates

Fischer Proof of the Structure of (+)-glucose



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Morrison - Boyd Organic Chemistry Slides Notes

CHE-310/311 Organic Chemistry I


Available for topics





Introductory notes and review of general chemistry

Methane

Homework #6

Alkanes

Stereochemistry

Problem sets on the web for the R/S system of specification of configuration

Alkyl halides

Alcohols

Ethers

Alkenes,syntheses

Alkenes,reactions

Stereospecific and stereoselective reactions

Supplemental homework

Problem sets on the web regarding stereoselective/stereospecific reactions

Dienes

Alkynes

Exam III

Alicyclics

Aromaticity/benzene

Electrophilic Aromatic Substitution

Problem sets on the web involving electrophilic substitution reactions

Arenes



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Organic Chemistry Chapter 5 Stereochemistry: Chiral Molecules

Chapter outline

http://members.aol.com/logan20/outline5.html

PPT slides

http://nlfaculty.dcccd.edu/logan/slides/chapter5/index.htm


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Sunday, September 14, 2008

Solomon Org. Chemistry Chapter 4 Alkanes and Cycloalkanes: Conformations of Molecules

Chapter Outline

http://members.aol.com/logan20/outline4.html

Nomenclature and Physical Properties of Alcohols and Ethers

http://members.aol.com/logan20/nom_alc.html

Slides

http://nlfaculty.dcccd.edu/logan/slides/chapter4/index.htm

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Solomon Organic Chemistry Ch. 3 Acids and Bases in Organic Chemistry

Chapter outline

http://members.aol.com/logan20/outline3.html

Slides

http://nlfaculty.dcccd.edu/logan/slides/chapter3/index.htm



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Solomon Organic Chemistry Chapter 2 Representative Carbon Compounds

Chapter 2 Outline

http://members.aol.com/logan20/outline2.html

Slides

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Solomon Org Chemistry Chapter 1 Carbon Compounds and Chemical Bonds

Outline and some lecture notes

http://members.aol.com/logan20/outline1.html


PPT Slides for Chapter 1

http://nlfaculty.dcccd.edu/logan/slides/chapter1/index.htm


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Web Links for Solomons book on Organic Chemistry

Web Links for Solomons book on Organic Chemistry


These web links, organized by chapter, provide more information about topics covered in the text and will help in your study of organic chemistry.



http://www.wiley.com/college/chem/solomons190950/weblinks.html

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Friday, September 12, 2008

Presentation - Chiral Atoms




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http://docs.google.com/Presentation?id=dg3h8m78_11cpckn6gb

Chiral Molecules - July Dec Revision

Chiral molecules

A molecule is said to be chiral if it lacks symmetry and its mirror images are not superimposable. To be chiral a molecule must lack symmetry, that is, a chiral molecule can not have any type or symmetry.

Carbon atoms with four sp3 hybridized orbitals can enter into up to four different bonds about the central carbon atom.
When the central carbon bonds with differing atoms or groups of atoms the carbon is termed an asymmetric carbon atom.

Bromochlorofluoromethane is an example of such a molecule. The central carbon, with four sp3 bonds oriented (pointing) to the corners of a tetrahedron, is bonded to a bromine, chlorine, fluorine and methane atoms. There is no symmetry to this molecule.

To explain things in a more simple way, Chiral molecules are like right hand left hand. Both hands have identical fingers but in different orientations. The little finger is in clockwise direction from the middle finger in right hand, where as the little is in the counterclockwise direction in the left hand. So you can fix a right hand to another person's left wrist. Right hand and left hand are different even though all the five diffetent fingers are more or less similar in both the hands.


Enantiomers are optical isomers. A chiral molecule will have enantiomers.


A solution in which both enantiomers of a compound are present in equal amounts is called a racemic mixture, or racemate.

Friday, September 5, 2008

Fluid - July Dec revision

There is continuity between the gaseous and liquid state. The term fluid is used for either liquid or a gas to recognize this continuity. A liquid can be viewed as a very dense gas. Liquid and gas can be distinguished only when the fluid is below its critical temperature and its pressure and volume lie under the dome (in isotherm) since in that situation liquid and gas are in equilibrium and a surface separating the two phases is visible.


Chapter: States of Matter




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