Compound containing Nitrogen

By Azeem

Nitro Compound

General method of preparation-1. Nitration of alkanes2. From alkyl halides3. From salts of α-halogeno carboxylic acid4. From primary amines5. From a-nitroalkenes(2methyl nitropropene)6. From oximes(aldoxime +O in trifluoroperoxy acetic acid)

Reaction of nitroalkane1. Reduction2. Hydrolysis3. Halogenation4. Reaction with nitrous acid5. Condensation with aldehydes and ketones

Nitro Compound

Classification of amines

Physical Properties of Amines• The methylamines (mono-, di-, tri-) and ethylamine

are gases at room temperature , other amines are liquid at room temperature.

• Amines are irritating to the skin, eyes, and mucous membranes and are toxic by ingestion.

• Aromatic amines are generally toxic. Amines are readily absorbed through the skin and affect both the blood and the nervous system.

• Amines B.P are higher than alkane but not in alcohol.

• Both amine and ammonia are produce basic aqueous solution.

• Amine and ammonia are weak base due to accepter of proton.

• NH3 + H2O → NH4 + OH• Increase mass decrease solubility. Colourless.

Physical Properties of Amines

Nomenclature of amines

Method of preparation of amines1. From alkyl halide: by ammonolysis2. From alkyl halide: Gabriel phthalimide

synthesis(alkylation of phthalimide)3. From oximes, alkyl cyanides, amides and nitro

compounds: by reduction(a) From oximes(b) From alkyl cyanide(alkyl nitriles)(c) From amides(d) From nitro compounds(e) From amides: by hoffman bromamide degradation

1. From alkyl halide: by ammonolysis

H-NH2

100˚C underpressure

2. From alkyl halide: Gabriel phthalimide synthesis

3. From oximes, alkyl cyanides, amides and nitro compounds: by reduction

a. From oximes

• Aldoxime or ketoximes are reduce by sodium and ethanol to primary amine.

• R- CH= N-OH + 4[H] → R-CH2-NH2 + H2O• Ketoxime.• Acetaloxime.

b. From alkyl cyanide(alkyl nitriles)

• Alkyl cyanide on reduction by Na and ethanol give primary amine.

• R-C ≡ N + 4[H] → R-CH2-NH2• Eg. Acetonitrile and Propanenitrile.

c. From amides

4[H]

d. From nitro compound

• Nitro compounds are reduced by tin(Sn) or iron and con HCl to corresponding primary amines.• R- NO2 + 6[H] → R- NH2 + 2H2O• Eg. Nitrobenzene.• Nitropropane.

e. Hoffman bromamide degradation

Reaction of Amines1. Basic nature of amines2. Action of nitrous acid (1⁰ amine, 2⁰ amine, 3⁰ amine)3. Acylation of amines4. Alkylation of amines: Hoffmann's exhaustive

alkylation5. Hoffmann elimination6. Hoffmann’s carbylamines test/ isocyanides test7. Reaction with arylsulphonyl chloride: Hinsberg’s test8. Electrophilic aromatic substitutiona) Bromination b) Nitration c) sulphonation

1. Basic nature of amines• R- NH2 + H+X → R-NH3

+X-

ammonium salts• R-NH3

+X- + NaOH → R-NH2 + NaX + H2O• This shows that the reaction is reversible.• C2H5-NH2 + HCl <==> C2H5-NH3

+Cl-

Ethylamine ethyl ammonium chloride

Aqueous solutions amines are basic, and they turn red litmus paper blue.R-NH2 + H-O-H R- NH3

+ + OH-

Weak base strongerbase

2. Action of nitrous acid

• Primary, secondary & tertiary amines react differently with nitrous acid.

• Since nitrous acid is unstable, it is prepared in situ(Latin- reaction mixture) at 273K- 278K.

• NaNO2 + HCl → NaCl + HNO2

• Except methyl and ethylamine, all primary amine give aliphatic diazonium salt.

• Primary amine: (HNO2) eg. AnilineR – NH2 + NaNO2 + 2HCl → [ R- N2

+Cl-] + NaCl + 2H2OAlkyl diazonium chloride

• Secondary amine: (HNO2)eg. diethylamineR2 – NH + NaNO2 + HCl → R2N-N=O + NaCl + 2H2O

N- nitroso dialkylamine• Tertiary amine: (HNO2)eg. triethylamineR3 – N + NaNO2 + HCl → [ R3- NH]+NO2

- + NaCltrialkyl ammonium nitrate

2. Action of nitrous acid

3. Acylation of amines

• Amine react with acyl chloride in presence of pyridine.

• R- NH2 + X-CO-R R- NH – CO –R + HX • Eg. Ethylamine• Silimalary reaction in acetic anhydride,• R- NH2 + (CH3- CO-)2OR-NH-CO-CH3 + CH3- COOH

Amines ethanoic anhydride alkyl acetamide

• Eg. Aniline

4. Alkylation of amines: Hoffmann's exhaustive alkylation

• R- NH2 R2NH R3N R4N+X-

» 2⁰ amine 3⁰ tetraalkyl ammonium halide

• Eg. Methylamine• Eg. Dimethanamine• Eg. N,N- dimethyl aniline

RXRX RX

5. Hoffmann elimination• Tetra alkyl ammonium halide on heating with moist Ag2O

form tetra-alkyl ammonium hydroxides.• This is deliquescent crystalline solid and basic in nature. (of a solid) tending to absorb moisture from the air and dissolve in it.• On heating undergo β-elimination to form alkene, tertiary

amine and water.• C2H5N-(CH3)3

+I- + AgOH C2H5-N+(CH3)3OH- + AgIEthyltrimethyl ammonium iodide

• C2H5-N+(CH3)3OH- CH2=CH2 + (CH3)3N + H2OEthyltrimethyl ammonium hydroxide

6. Hoffmann’s carbylamines test/ isocyanides test

• R-NH2 + CHCl3 + 3KOH → R- NC + 3KCl + 3H2O• Eg. Ethylamine• and aniline.

7. Reaction with arylsulphonyl chloride: Hinsberg’s test

8. Electrophilic aromatic substitution

• Bromination

Bromination

Nitration

Nitration

• Aniline on acetylation on heating 298K.

Sulphonation

Preparation of Diazonium Salt’s

Reaction of Diazonium salts

A. Reaction involving replacement of diazonium group

1. Replacement by –Cl, -Br, -CN: sandmeyer rxn2. Gettermann reaction: replacement by –Cl, Br:3. Balz- Schiemann: Replacement by –F.–I,-H, -

OH, -NO2B. Reactions involving retention of diazonium Group: Coupling reaction

Replacement by –Cl, -Br, -CN: sandmeyer rxn

Cl

2. Gatterman reactions

diazonium groups are replaced with Cl or Br by treating the diazonium salt solution with halogen acid in the presence of copper powder.

3. Replacement of –I

• Diazonium group may be replaced by iodine by treatment with potassium iodide.

4. The Schiemann reactionthe diazonium group is replaced by hydrogen after treatment with mild reducing agents such as hypophosphorous acid (or) ethanol.

5. Replacement of -OH

Azo coupling Reaction

Benzendiazonium chloride + phenol give p- hydroxyazobenzene.

Importance of Diazonium salts

• Arene diazonium salts are intermediates to introduce –F, -Cl, -Br, -I, -CN, -H, -OH, NO2 groups in aromatic ring.

• Azo comounds are strongly coloured(red, yellow, orange, blue) and used as dyes.