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Organic Compounds containing Nitrogen is a quite significant topic in JEE Main Chemistry. It holds a crucial place within the broader subject area of General Organic Chemistry and about 1-2 questions get asked from the section that bear a total of around 4 marks. Thus, the complete weightage of this chapter is about 1-2% in JEE Main. If you study the theory from this chapter thoroughly, the questions are generally pretty simple to answer and score. A few of the concepts tested from Organic Compounds containing Nitrogen are - Amines, their Properties, and Reactions. Read Complete JEE Main Syllabus
Read the article below to access study notes on Organic Compounds containing Nitrogen to help you with JEE Main preparation -
Must Read Study Notes
The nitrogen is in sp3 hybridization with 3 sigma bonds and 1 lone pair of electrons for amines. Amines have tetrahedral geometry. However, the bond angle within their structure is usually lower than 109.50 as the nitrogen atom holds a lone pair of electrons that lessens the bond angle.
a) Aliphatic Amine
Basic Strength: NH3 < RNH2 < R2NH < R3N,
b) Aromatic Amine
Basic Strength: NH3 > Ar- NH2 > Ar2- NH2
The benzene ring lowers the electron density over the N atoms because of the resonance effect.
Amines can be made with the use of the methods given below -
Reduction of Nitro Compounds
Reduction happens with hydrogen gas for nitro compounds when finely divided nickel, palladium or platinum is present to give amines. Also, reduction with metals in an acidic medium provides amines.
Ammonolysis (Hoffmann’s method)
Ammonolysis is the process of cleavage of the C-X bond by ammonia molecule.
The order of reactivity of halides with amines is given as, RI >RBr > RCl.
Reduction of Nitriles
Nitriles when reduced with LiAlH4 or catalytic hydrogenation give primary amines. This method is utilized for the preparation of amines that contain one carbon atom greater than the original amine.
Reduction of Amides
Amides when reduced with LiAlH4 produces amines.
Acylation is the process of introduction of an acyl group (R–CO–) into the molecule. The reaction is formed when a stronger base than the amine is present, like pyridine, that eliminates the HCl created and moves the equilibrium towards the product side.
When heated, aliphatic and aromatic primary amines with chloroform and ethanolic KOH, produce isocyanides or carbylamines that do not have a foul smell. Secondary and tertiary amines do not display such a reaction. This reaction has been utilized as a test for primary amines.
Primary aliphatic amines when reacted with nitrous acid produce aliphatic diazonium salts. Aromatic amines when treated with nitrous acid at a low temperature give diazonium salts that can be used in the synthesis of a range of aromatic compounds. Secondary and tertiary amines are seen to react with nitrous acid in another manner.
Hinsberg’s reagent or benzenesulfonyl chloride (C6H5SO2Cl) shows reaction with primary amines and secondary amines to produce sulphonamides. Primary amine react with benzenesulfonyl chloride to give N-ethylbenzenesulphonyl amide.
With secondary amines, N,N-dimethyl-benzenesulfonamide is produced.
N, N-diethylbenzene sulphonamide does not have any H atom linked to the nitrogen atom. Therefore, it is not acidic and is thus insoluble in alkali. Tertiary amines have no reaction with benzenesulfonyl chloride. The reaction of amines with benzene sulphonyl chloride in another manner is utilized for the differentiation of primary, secondary, and tertiary amines.
Ortho- and para-positions of the -NH2 group turn into centres which have a high electron density. Thus, the -NH2 group is ortho and para directional and is also a strong activating group.
Aniline has a reaction with bromine water at room temperature to produce a white precipitate of 2, 4, 6-tribromoaniline.
Nitric acid is a nitrating agent and a good oxidising agent. Therefore, the direct oxidation of aromatic amines is not beneficial because it provides tarry oxidation products along with a few nitro derivatives. In a powerful acidic medium, aniline gets protonated to give the anilinium ion that is meta directing. Hence, apart from the ortho and para derivatives, a good amount of meta derivative also gets produced.
Aniline when reacted with sulphuric acid gives anilinium hydrogen sulphate. This, when heated with sulphuric acid at 453-473K, produces p-aminobenzene sulfonic acid as the significant product.
The diazonium group is quite a good leaving group which gets substituted by other groups like Cl-, Br-,I-,CN- and OH- that displace nitrogen from the aromatic ring. The nitrogen that gets released from the reaction mixture leaves as a gas.
This reaction is known as the Sandmeyer reaction. Here, the nucleophiles such as Cl-,Br- and CN- can be conveniently introduced in the benzene ring when the Cu(I) ion is present.
In an alternative manner, chlorine or bromine could also be added in the benzene ring by treating the diazonium salt solution with respective halogen acid when Cu powder is present. This is known as the Gatterman reaction.
Amines are classified according to the number of alkyl or aryl groups that are linked to the nitrogen atom.
Classification of amines
Reduction of Nitro Compounds: Here, the nitro compounds get reduced by the (H2 / Pd) reagent to form amines.
Reduction of Nitriles: Here, the nitriles get reduced to amines by one other equally powerful reducing agent like H2 / Ni.
Hoffmann bromamide degradation reaction: Here, the amide gets treated with bromine when an aqueous solution of NaOH is present There is a conversion of amide to a primary amine that has 1 carbon lower than the amide.
RNH2 + R'COCl→ R'CO NHR an N-substituted amide
R2NH + R'COCl → R'CO.NR2 an N,N disubstituted amide
b) Benzoylation (Schotten Baumann Reaction)
Primary amine has a reaction with benzoyl chloride to produce the acylated product
c) Carbylamine Reaction (Given Only by Primary Amines)
C2H5NH2 + CHCl3 + 3KOH → C2H5NC + 3KCl + 3H2O
C6H5 NH2 + CHCl3 + 3KOH → C6H5NC + 3KCl + 3H2O
d) Action with Aldehyde and Ketone
e) Hofmann Mustard Oil Reaction
f) Reaction with Carbonyl Chloride
C2H5 – NH2 + COCl2 → C2H5NCO + 2HCl
g) Hofmann Elimination
When a quaternary ammonium hydroxide gets strongly heated at125° or higher, it decomposes to give water, a tertiary amine and an alkene.
h) The diazonium salts of amines
i) Reaction of Tertiary amines with Nitrous acid
When a tertiary aliphatic amine gets blended with nitrous acid, an equilibrium gets formed between the tertiary amine, its salt, and an N-Nitroso Ammonium compound.
j) Coupling Reactions of Arene Diazonium Salts
k) Ring Substitution in Aromatic Amines
l) Aniline -X rearrangement
These kinds of compounds are not very stable. Therefore, the group X migrates primarily at the p-position.
1. Fisher-Hepp rearrangement
2. Phenylhydroxylamine - p-aminophenol rearrangement.
Primary amine: RNH2 + C6H5SO2Cl ¾® C6H5– SO2 – NH – R + HCl
C6H5– SO2 – NH – R : N-alkyl benzene sulfonamides
(Dissolves in NaOH because of the acidic H-attached to Nitrogen)
Tertiary amine : Tertiary amines do not have a reaction with Hinsberg’s reagent.
The mixture of amines gets treated with diethyl oxalate that forms a solid oxamide with primary amine, a liquid oxime ester with secondary amine. The tertiary amine has no reaction.
Primary amine gets treated with a strong base when chloroform is present. An isocyanide gets produced which has a very foul odour.
Secondary amine gets converted into nitrosamine when treating the amine with nitrous acid. The resultant solutions are warmed with phenol and concentrated H2SO4. A brown or red colour gets formed first and soon, it turns blue and then green. The colour further changes to red on dilution and to greenish blue when treated with alkali.
Tertiary arylamines react with nitrous acid to produce an o-nitroso aromatic compound
Question: 1 Compare the basicities of
a) H2C = CHCH2NH2, CH3CH2CH2NH2 and HC º CCH2NH2, and
b) C6H5CH2NH2, cyclohexyl – CH2NH2 and p-NO2C6H4CH2NH2.
a The major difference between these three bases is the type of hybrid orbital utilized by Cb — the more s character it possesses, the more electron-withdrawing through induction and base weakening will it be. The HO situations are H2C = CbHCH2NH2(sp2), CH3CbH2CH2NH2(sp3), and HC º CbCH2NH2(sp). The rising order of electron–attraction is propargyl > allyl > propyl >, and the decreasing order of basicity is CH3CH2CH2NH2> H2C = CHCH2NH2 > HC º CCH2NH2
b) The decreasing order is,
The Cb is cyclohexyl – CH2NH2 utilizes sp3 HO’s while the Cb in the benzylamines makes use of the sp2 HO’s. The electron-withdrawing p-NO2 makes the phenyl ring more electron–withdrawing and base weakening.
Question: 2 A compound X that has seven carbon atoms when treated with Br2 and KOH produces Y. Y forms carbylamine test and after diazotization and coupling with phenol forms s azodye. X is?
(B) CH3 – (CH2)5 – CONH2
(C) CH3 –C(CH3)2- CH2 – CH2 – CONH2
(D) O – CH3 – C6H4NH2
Question: 3 A compound (A) when reacting with PCl5 and then with NH3 gives (B), (B) when treated with Br2 and KOH gives (C). (C) when treated with NaNO2 and HCl at 0°C and the boiling with water gives o-cresol. Compound A is?
(A) o-toluic acid
(C) o-bromo toluene
(D) m-toluic acid
|Week 1 (June 7 to 14)||Physical Chemistry has the highest weightage in JEE Main Chemistry. More important chapters from this topic are Electrochemistry, Equilibrium, and Atomic Structure which have to be studied first. Then, study low weightage chapters such as Surface Chemistry and Solid State. Choose two chapters every day and read all the necessary concepts and reactions.|
|Week 2 (June 14 to 20, 2020)||Go through Organic Chemistry for this week. Give more time to chapters which are most important like Aromatic Compounds, Alkyl Halides, Alcohol, and Ether. Then, study chapters which are less important like Biomolecules and Carbonyl Compounds.|
|Week 3 (June 21 to 27, 2020)||Read Inorganic Chemistry this week. Begin by studying the most important chapters like p Block, s Block, and Chemical Bonding. Study less important chapters like Metallurgy and Qualitative Analysis.|
|Week 4 (June 28 to -July 4, 2020)||Read through your study notes, reactions, and important concepts. Attempt previous years’ question papers for more practice. Choose questions from the Chemistry section and answer them as fast as you can. It is recommended that you do this within 45 minutes to 1 hour.|
|Week 5 (July 5 to 11, 2020)||Answer mock tests each day this week.|
|Week 6 (July 12 to 17, 2020)||Revise basic concepts and reactions from every chapter.|
|JEE Main Exam Week (July 18 to 23, 2020)||Go through the analysis of the ongoing JEE Main papers|