JEE Main Chemistry Revision - Concepts and Definitions

Read Every Day 10 Points and Think of the other points that are implied by them. 

This process will help you to complete intensive study of all the concepts  of the subject by the time you appear for JEE Main in April 2020.

12 January 2019

Haloalkanes and Haloarenes

JEE Syllabus

UNIT 22: ORGANIC COMPOUNDS CONTAINING HALOGENS

General methods of preparation, properties and reactions; Nature of C-X bond; Mechanisms of substitution reactions. Uses; Environmental effects of chloroform - iodoform.

1. The groups which possess two nucleophilic centres are called ambident nucleophiles.

Explanation: An ambident nucleophile has "teeth" on two sides.

It can attack from two different places and form two different products.

For example, the thiocyanate ion, SCN⁻, is a ambident nucleophile. It is a resonance hybrid.

Both the S  and the N  atoms can act as nucleophiles.

So, the SN2  reaction of an alkyl halide with SCN⁻  often leads to a mixture of an alkyl thiocyanate and an alkyl isothiocyanate.

R-X+SCN⁻→X⁻   + R-SCN          + R-NCS
                alkyl            alkyl
                thiocyanate      isothiocyanate
https://socratic.org/questions/what-is-an-ambident-nucleophile


2. The rate of reaction depends on the concentration of both alkyl halid and base, the reation is known as SN2 reactions.

3. The rate of reaction depends on the concentration of alkyl halides, the reaction is known as SN1 reaction.

4. The order of reactivity of alkyl halides for SN1 reactions

3 degree halide > 2 degree halide > 1 degree halide > CH3X
(tertiary)              (secondary)           (primary)

5. The order of reactivity of alkyl halides for SN2 reactions

3 degree halide < 2 degree halide < 1 degree halide < CH3X

6.  In SN1 and SN2 mechanism, the reactivity of halides follows the order

R-I > R-Br > R-Cl > R-F

7. If all the substituents attached to a carbon are different, that carbon is called asymmetric (or) Chiral carbon or stereocentre.

8. The stereo isomers related to each other as non-super imposable images are called enantiomers.

9. A mixture containing two enantiomers in equal proportions will have zero optical rotation, as the rotation due to one isomer will be exactly cancelled by the rotation due to the other isomer. Such a mixture is known as racemic mixture or racemic modification.

10. The process of conversion of enantiomer into a racemic mixture is known as racemisation.


Key words:  ambident nucleophiles, SN2 reactions, SN1 reaction, The order of reactivity of alkyl halides for SN1 reactions (degree of halides),  The order of reactivity of alkyl halides for SN2 reactions(degree of halides), order of  reactivity of halides (based on halogen), asymmetric (or) Chiral carbon or stereocentre, enantiomers, racemic mixture or racemic modification, racemisation.

13 January 2020

11. SN2 reactions of optically active halides are accompanied by inversion of configuration.

12. SN1 reactions are accompanied by racemisation.

13. Finkelstein reaction - The reaction of alkyl chloride (or) bromide with NaI in dry acetone gives Alkyl iodides.

14. Swarts reaction -The reaction of alkyl chloride (or) bromide with metal flourides like AgF, Hg2F2, CoF2, SbF3 on heating gives alkyl fluorides.

15. Haloalkane reacts with KCN to form alkyl cyandie as main product where haloalkane reacts with AgCN to form alkyl isocyanide as the main product.

16. Sandmeyer's reaction - The reaction of benzene diazonium salt with cuprous chloride (or) bromide and HCl gives chlorobenzene or bromobenzene.

Reactions of Cholorobenzene

17. Cholorobenzene reacts with chlorine in presence of AlCl2 gives 1,4-dichlorobenzene as a major product, and 1,2 -dichlorobenzene as a minor product.

18. Cholorobenzene reacts with nitration mixture and gives 1-chloro-4-nitrobenzene as a major product and 1-chloro-2-nitrobenzene as a minor product.

19. Cholorobenzene reacts with CH3Cl in presence of AlCl3 adn gives 1-chloro-4-methylbenzene as a major product and 1-chloro-2-methyl benzene as a minor product.

20. Cholorobenzene reacts with CH3COCl in presence of AlCl3 and gives 4-chloro-acetophenone as a major product and 2-chloro-acetophenone as a minor product.

14 January 2020

21. Fittig reaction: Cholorobenzene reacts with sodium in presence of dry ether - gives diphenyl.

22. Wurtz-Fittig reaction: Cholorobenzene, alkyl halide and sodium react in presence of dry ether and give alkyl benzene.

23. DDT = P, p1-dichlorodiphenyltrichloroethane

24. Grignard reagent (RMgX): Obtained by the reaction of haloalkanes with magnesium metal in dry ether.

25. Freons (CCl2F2) are chlorofluoro compounds of methane and ethane.

26. In dehydrohalogenation reactions, the preferred product is that alkene which has the greater number of alkyl groups attached to the doubly bonded carbon atoms.

Organic Compounds with Functional Groups OH and CHO

JEE Syllabus

UNIT 23: ORGANIC COMPOUNDS CONTAINING OXYGEN

General methods of preparation, properties, reactions and uses

ALCOHOLS, PHENOLS AND ETHERS

Alcohols: Identification of primary, secondary and tertiary alcohols; mechanism of dehydration.

Phenols: Acidic nature, electrophilic substitution reactions: halogenation, nitration and sulphonation, Reimer – Tiemann reaction.

Ethers: Structure.

Aldehyde and Ketones: Nature of carbonyl group;Nucleophilic addition to >C=O group, relative reactivities of aldehydes and ketones; Important reactions such as – Nucleophilic addition reactions (addition of HCN, NH3 and its derivatives), Grignard reagent; oxidation; reduction (Wolff Kishner and Clemmensen); acidity of α – hydrogen, aldol condensation, Cannizzaro reaction, Haloform reaction; Chemical tests to distinguish between aldehydes and Ketones.

Carboxylic acids: Acidic strength and factors affecting it.

Alcohols and Phenols

1. Methanol (CH3OH) is referred to as wood spirit.

Alcohol from alkenes

2. Alkenes react with water in the presence of acid as catalyst to form alcohols.

Mechanism of alcohol formation

3. Protonation of alkene to form carbocation by electrophylic attack of H3O+.

4. Nucleophylic attack of water on carbocation.

5. Deprotonation to form an alcohol

Key words:   Fittig reaction, Wurtz-Fittig, DDT,  Grignard reagent , Freons,  preferred product in dehydrohalogenation reactions of halides, wood spirit., Alcohol from alkenes ,


15 January 2020

6. Diborane (BH3)2 reacts with alkenesto give trialkyl boranes as addition product.

7. Trialkyl borane is oxidized to  alcohol by hydrogen peroxide in the presence of acqueous sodium hydroxide.

8. With sodium borohydride (NaBh4) or lithiumaluminium hydride (LiAlH4), aldehydes yield primary alcohols. Ketones give secondary alcohols.

9. Primary (1 degree), secondary (2 degree) and tertiary (3 degree) alcohols are distinguished by Lucas test.

Preparation of Phenol

10. Chlorobenzene is fused with NaOH at 623K and 320 atmospheric pressure.  ... Phenol is obtained by acidification of sodium phenoxide.

11. Benzene is sulphonated with oleum and benzene sulphonic is acid formed. The acid is converted to sodium phenoxide on heating with molten sodium hydroxide. Phenol is obtained by acidification of sodium phenoxide.

High boiling points of alcohols

12. The high boiling points of alcohols are mainly due to the presence of intermolecular hydrogen bonding in them which is not present in ethers and hydrocarbons.

13. Propanol has higher boiling point than that of hydrocarbon n-butane due to intermolecular hydrogen bond.

Solubility of alcohols and phenols

14. Solubility of alcohols and phenols in water is due to their ability to form hydrogen bonds with water molecules.

15. The solubility decreases with increase in size of alkyl/aryl groups. Several lower molecular mass alcohols are misible with water in all proportions.

16 January 2020

Acidic nature of phenol.


16. The reactions of phenol with metals (sodium, alumimium) and sodium hydroxide indicate its acidic nature.

For details read: Acidic nature of phenols

17. The hydroxyl group, in phenol is directly attached to the sp2 hybridized carbon of benezene ring which acts as an electron withdrawing group.

18. The reaction of phenol with acqueous sodium hydroxide indicates that phenols are stronger acids than alcohols and water.

19. Due to the higher electronegativity of sp2 hybridised carbon of phenol to which -OH is attached electron density decreases on oxygen.

20. The presence of electron withdrawing groups such as nitro group, enhances the acidic strength of phenol.

21. The effect is more pronounced when withdrawing group is present at ortho and para positions. It is due to the effective delocalisation of negative charge in phenoxide ion.

Oxidizing alcohols 

22. Strong oxidizing agents such as potassium permanganate are used for getting carboxylic acids from alcohols directly.

23. CrO3 in anhydrous medium is used as the oxidizing agent for the isolation of aldehydes.

24. A better reagent for oxidation of primary alcohols to aldehydes in good yield is pyridium chlorochromate (PCC), a complex of chromium trioxide with pyridine and HCl.

25. The -OH group attached to the benzene ring activates it towards electrophilic sustituion. Also it directs the incoming group to ortho and para positions in the ring as these positions become electron rich due to the resonance effect caused by -OH group.


17 January 2020


26. The ortho and para isomers can be separated by steam distillation.

27. Kolbe's reaction: Phenol is treated with sodium hydroxide and carbon dioxide to from salicylic acid.

28. Reimer - Tiemann reaction:Phenol reacts with chloroform in the presence of sodium hydroxide to form salicylaldehyde.

29. Reduction of phenol with zinc dust forms benzene.

30. Oxidation of phenol with chromic acid produces a conjugated diketone known as benzoquinone.

31. Williamson synthesis:

32. Anisole reacts with the alkylhalide and acyl halide in the presence of anhydrous aluminium chloride as catalyst. The alkyl and acyl groups are introduced at ortho and para positions in the resultant  products.

33. Nitration: Anisole reacts with a mixture of concentrated sulphur amd nitric acid to yield a mixture of ortho and para nitroanisole.


18 January 2020

Aldehydes, Ketones and Carboxylic Acids

1. Friedel-craft acylation: Benzene is treated with acetylchloride in the presence of AlCl3 to form acetophenone.

2. Cannizaro reaction: Aldehydes which do not have α-hydrogen atom react with concentrated sodium hydroxide (NaOH) or potassium hydroxide (KOH) in such a way that one molecule get oxidized to acid and the second molecule gets reduced to alcohol.

Note two molecules of aldehyde participates in the reaction.

This self oxidation-reduction under the influence of a base is known as the Cannizzaro's reaction.

Formaldehyde does not possess α-hydrogen atom and therefore undergoes Cannizzaro's reaction. Acetaldehyde does not give this reaction.

3. Aldol Condensation: Aldehydes and ketones containing α-hydrogen (H-atoms attached to the C-atom adjacent to the carbonyl group)undergo condensation in the presence of dilute alkali.

In the resulting compound both aldehyde group and alcohol group are present.

acetaldehyde and acetone undergo aldol condensation.
Formaldehyde, banzaldehyde do not undergo aldol condensation.

4. Cross aldol condensation: Aldol condensation  carried out between different aldehydes (or) ketones. In this process 4 products are obtained.

5. Acid salts are heated with sodalime loose CO2 to form hydrocarbons.

6. HVZ reaction:

7. Carbonyl compounds participate in nucleophylic addition reactions.

8. Carbonyl compounds are treated with HCN to form Cynohydrins.

9. Aldehydes react with one molecule of alcohol in the presence of dry HCL and form alkoxy alcohols. It is called hemiacetal.

10. Aldehydes react with two  molecules of alcohol and form dialkoxy compounds.  It is called acetal.


19 January 2020

11. Formation of semicarbozone:

12. Formation of oxime:

JEE Syllabus topic: Carboxylic acids: Acidic strength and factors affecting it.

13. Presence of electron withdrawing groups increases acidic nature of Carboxylic Acids.

14. Presence of electron releasing groups decreases acidic nature of Carboxylic Acids

15. Feling's reagent.

16. Fehling test

17. Tollen's reagent

18. Tollen's test

19. In benzoic acid electrophylic substitution takes place at meta position.

20. Acetic acid is treated with PCl3/PCl5 to form Benzamide.

20 January 2020

21. Formation of Benzamide

22. Increasing order of acidic strength of various benzoic acids.

23. Decreasing order of acidic strength of given carboxilic acids

Organic Compounds Containing Nitrogen - Amines

JEE Syllabus

UNIT 24: ORGANIC COMPOUNDS CONTAINING NITROGEN

General methods of preparation, properties, reactions and uses

Amines: Nomenclature, classification, structure, basic character and identification of primary, secondary and tertiary amines and their basic character.

Diazonium Salts: Importance in synthetic organic chemistry.


1. What are amines?

2, Preparation of aniline.

3. Ammonolysis

4. Reactity of halides with amines - order

5. Primary amines from nitriles

6. Primary amines from amides

7. Gabriel phthalimid synthesis

21 January 2020

8. Hoffman bromamide degradation reaction.

9. Boiling points of different amines.

10. Order of basic nature of amine (Remember acidic nature of phenols)

11. Amines behave as Lewis bases.

12. Alkylation of amines.

13. Acetylation of amines.

14. Benzoylation of amines

15. Carbylamine reaction

16. Amines - nitrous acid reation

17. Diazotisation


22 January 2020

18. Hinsberg reagent

19. Formation of sulphonamide

20. reaction of tertiary amines

21. Ortho and para directing and ring activating group

22. 2,4,6,  tri bromo aniline formation

23. Nitration reaction of aniline

24. Zwitterion

25. Aniline and Friedal crafts reaction

26. Benzene diazonium chloride.

27. Diazonium salt general formula

23 January 2020

28.Sandmeyer reaction

29. Gatterman reaction

Cyanides

1. Formation of cyanides - Aldoximes are dehydrated by acetic anhydride.

2. Hydrolysis of isocyanides

3. Cyanides reaction with Grignard reagent.

4. Cyanides reaction with LiAlH4

5. Ioscyanides reduction with H2/Ni

6. Oxidation of isocynaides


24 January 2020

Inorganic Chemistry

General Principles of Metallurgy

1. Mineral

2. Ore

3. Flux

4. Gangue

5. Slag

6. Matte

7.  Concentration of Ore

8. Froth flotation process


10. Roasting: Process of heating in presence of air.


25 January 2020

11. Calcination

12. Electrometallury

13. Blast furnace - Chemical reactions

14. Extraction of coppoer from copper pyrites

15. Electrolytic refining of copper

16. Ore of aluminium

17. Electrolytic reduction of pure alumina.

18. General methods of refining

19. Role of cryolite

20. Fractional crystallization

26 January 2020

21. Vapour phase refining

22. Composition of alloys. - Brass

23. Uses of metal zinc

24. Uses of metal copper

25. Uses of metal iron

26. Uses of metal aluminium

27. Uses of cast iron

28. Uses of wrought iron

29. Uses of nickel steel

30. Uses of stainless

27 January 2020

P-Block Elements




Updated 20 January 2020,  17 January 2020,