Nitro compounds

The NO2 group attached with organic chain is called as nitro functional group. All the compounds containing the nitro functional group are called as organic nitro compounds.

1. Nitro Compounds DR . TANUJA NAUTIYAL DEPT OF CHEMISTRY NORTHERN INDIA ENGINEERING COLLEGE

2. Organic compounds containing nitrogen can be broadly classified into two groups . Compounds containing nitro functional group - NO 2 Compounds containing amine functional group -NH 2  and their derivatives. In this nitro compounds are primary source of organic compounds with functional group -NO 2  to start the synthesis of many other important compounds Nitro Compound

3. The NO 2  group attached with organic chain is called as nitro functional group. All the compounds containing the nitro functional group are called as organic nitro compounds. They are classified as Aliphatic nitro compounds Aromatic nitro compounds Nitro Compound

4. Aliphatic Nitro Compounds If the nitro functional group is attached with aliphatic carbon chain it is called as aliphatic nitro compound. They are weakly acidic due to their azinitro form and they are soluble in alkalies and can undergo condensation reaction with aldehydes . CH 3 -NO 2  - Nitro methane . 

5. Aromatic Nitro Compounds If the nitro functional group is attached with benzene ring it is called as aromatic nitro compound. All aromatic nitro compounds are yellow colored liquids which may change to dark brown color due to oxidation .

6. The NO 2  group is called as nitro group. It is electron withdrawing group due to its  -Inductive effect   as well as  -Resonance effect . Nitro Compound

7. Nomenclature of Nitro Compounds Organic compounds containing  nitro -NO 2  functional group are called as nitro compounds . They are obtained by replacing one or more hydrogen in the hydrocarbon with nitro group. Here, the nitrogen is directly attached to the carbon atom in the organic chain. 

8. Nomenclature of Nitro Compounds The general formula of nitro compounds is Nitro compounds are named by prefixing the nitro with the root alkane name with the locant . CH 3 NO 2  is amino methane CH 3 -CH(NO 2 )-CH 3  is 2-nitropropane

9. General method of preparation Nitration of alkanes From alkyl halides From salts of α - halogeno carboxylic acid From primary amines From a- nitroalkenes From oximes

10. By direct nitration of alkanes Alkanes are treated with nitrating mixture (fuming nitric acid) with concentrated sulfuric acid to give nitro compounds. This method will not give good yield in case of aliphatic nitro compounds, but will give best yield for aromatic nitro compounds like nitro benzene. Ethane on nitration gives nitro ethane. CH 3 -CH 3  + HNO 3 /H 2 SO 4   →  CH 3 -CH 2 -NO 2

11. From alkyl halides By treating iodoalkanes with silver nitrite Iodo alkanes on reacting with silver nitrite give nitro compounds. This method will not give good yield for nitro benzene. But all the aliphatic nitro compounds can be prepared by this method.   For example iodoethane on treating with silver nitrite gives nitroethane . CH 3- CH 2 -I + AgNO 2   →  CH 3 -CH 2 -NO 2  + AgI

12. By treating amines with alkaline KMnO4 Tertiary amines on treating with alkaline KMnO 4   gives tertiary nitro compounds. This method works only with tertiary amines. 

13. Physical Properties of Nitro Compounds Aliphatic nitro compounds are mostly gaseous in nature and higher members are liquids. Aromatic nitro compounds are yellow color liquids which intensified to brown color by time. They are polar due to the presence of nitro group.

14. Isomerism in Nitro Compounds The isomerism exhibited by organic nitro compounds can be classified into the following types. 1. Chain isomerism Compounds having same molecular formula and difference in the nature of carbon chain is called as chain isomers. For example 1-nitro butane and 2-methyl 1-nitro propane. CH 3 -CH 2 -CH 2 -CH 2 -NO 2  CH 3 -CH(CH 3 )-CH 2 -NO 2

15. 2. Position isomerism Compounds having same molecular formula and difference in the position of attachment of functional group is called as position isomers. For example 1-nitro propane and 2-nitro propane. CH 3 -CH 2 -CH 2 -NO 2   CH 3 -CH(NO 2 )-CH 3 Isomerism in Nitro Compounds

16. 3. Functional group isomers Nitro compounds are functional group isomers for nitrite compounds in which the oxygen is bonded with the carbon chain. The following diagram explains the difference between nitro methane and methyl nitrite . Isomerism in Nitro Compounds

17. 4.  Tautamerism In solution the nitro form is in equilibrium with azinitro form. The azinitro form is acidic in nature and hence nitro methane is soluble in alkalis.  Isomerism in Nitro Compounds

18. Nitro compounds undergo tautomerism in solution to azinitro form, which is acidic in nature . Hence , all the nitro compounds are weakly acidic in nature.  Chemical Properties of Nitro Compounds

19. They dissolve in bases to give salts and can be regenerated by adding a stronger acid like HCl .  Similarly they can be reduced to amino compounds in acidic or basic medium. Chemical Properties of Nitro Compounds

20. Reaction of nitroalkane Reduction Hydrolysis Halogenation Reaction with nitrous acid Condensation with aldehydes and ketones Chemical Properties of Nitro Compounds

21. 1 . Reduction of aliphatic nitro compounds Aliphatic nitro compounds can be reduced to amines by treating with Sn / HCl . This is the effect way to convert nitro compounds to amines. CH 3 NO 2   →→  CH 3 NH 2 Chemical Properties of Nitro Compounds

22. Aliphatic nitro compound can be reduced to hydroxyl amines by treating with diborane . CH 3 NO 2   →→  CH 3 NHOH Aliphatic nitro compounds are reduced to oximes using stannous chloride. CH 3 NO 2   →→  CH 3 -N = OH Chemical Properties of Nitro Compounds

23. Reduction of aromatic nitro compounds Nitro benzene can be reduced to aniline by Sn / HCl .  On treating with Raney Nickle , nitro benzene is reduced to phenyl hydroxylamine .

24. Uses of nitro compounds They are useful intermediates in the preparation of amino compounds and diazonium salts which are synthetic important materials to prepare almost all organic compounds. Nitro benzene is used in shoe and floor polishes. It is also used in paint and solvents and to mask unpleasant odor in chemicals. They are used to prepare the azo -dyes and in soil sterility. It is used in the manufacture of Paracetamol (a popular analgesic)

25. THANK YOU DR . TANUJA NAUTIYAL DEPT OF CHEMISTRY NORTHERN INDIA ENGINEERING COLLEGE