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Nitrosoalkanes

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Nitrosoalkanes The nitrosoalkanes contain a nitroso-group, マN=O, directly attached to a carbon atom. They are named as the nitroso-derivatives of the corresponding alkanes, e.g., (CH 3 ) 3 CNO                 2-methyl-2nitrosopropane General methods of preparation 1.  By the addition of nitrosyl chloride or bromide to alkenes, whereby alkene nitrosohalides are formed: CH 2 =CH 2    +    NOCl    ⟶     ClCH 2 CH 2 NO    (2 mol) ⟶    (ClCH 2 CH 2 NO) 2 2.  By the action of nitrous acid on certain types of compounds, e.g., secondary nitroalkanes. 3. By the oxidation of primary amines containing a tertiary alkyl group with e.g., Caro’s acid (peroxy-(mono) sulphuric acid): R 3 CNH 2    +    2[O]      (H 2 SO 4 ) ⟶     R 3 CNO   +   H 2 O On the other hand, Emmons (1957) has prepared primary, secondary and tertiary nitroso-compounds by oxidation of amines with neutralized peracetic acid in methylene dichloride (yield: 33-80 per cent). N-Substituted hydrox
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Nitroalkane

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Nitroalkane The nitroalkanes are colorless (when pure), pleasant-smelling liquids which are sparingly soluble in water. Most of them can be distilled at atmospheric pressure. Nomenclature The nitroalkanes are named as nitro-derivative of the corresponding alkane, the positions of the nitro-groups being indicated by numbers, e.g. CH 3 NO 2                                              nitromethane            NO 2     NO 2          |            | CH 3 CHCH 2 CHCH 2 CH 3                      2,4-dinitrohexane The nitroalkanes, the structure of which is RNO 2 , are isomeric with the alkyl nitrites, RONO. The evidence that may be adduced for these respective formulas is to be found in the study of the reactions of these two groups of compounds. It is, however, worthwhile at this stage to mention the reaction which most clearly indicates their respective structures, viz., reduction. When alkyl nitrites are reduced, an alcohol and ammonia or hydroxylamines are formed. Th
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Cyanic acid

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Cyanic acid Cyanic acid, HNCO. Urea, on dry distillation, gives cyanuric acid : 3CO(NH 2 ) 2     ⟶      H 3 N 3 C 3 O 3    +    3NH 3 Cyanuric acid is a colorless, crystalline solid, not very soluble in water, and is strongly acid, reacting as a mono-, di- and tribasic acid. It has a cyclic structure (a triazine derivative) and X-ray analysis indicates that the acid is best represented as a resonance hybrid. When cyanuric acid is heated, it does not melt but decomposes into cyanic acid vapour which, when condensed below 0 o C, gives a colorless condensate: H 3 N 3 C 3 O 3     ⟶      3HNCO Cyanic acid is a colorless, volatile, strongly acid liquid which above  0 o C , readily polymerises to cyanuric acid and cyamelide , (HNCO) n . Aqueus solutions of cyanic acid rapidly hydrolyse to give carbon dioxide and ammonia: HNCO    +    H 2 O      ⟶      CO 2    +    NH 3 There are two possible structures for cyanic acid, H-O-C = N and H-N=C=O. There is very lit
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Cyanamide

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Cyanamide Cyanamide, m.p.42 o C, may be prepared by the action of ammonia on cyanogens chloride: ClCN    +    NH 3     ⟶      NH 2 CN    +    HCl It is also readily prepared by the action of water and carbon dioxide on calcium cyanamide. Cyanamide is converted into guanidine (q.v.) by ammonia and into thiourea (q.v.) by hydrogen sulphide. When cyanamide is melted it forms the dimer dicyandiamide , (NH 2 ) 2 C=NCN, and the trimer melamine, which is a cyclic compounds. X-ray analysis has shown that all the C-N bond lengths are the same. This can be explained on the assumption that melamine is a resonance hybrid of the amino-form ( cf. cyanuric acid). Melamine is manufactured by heating urea and passing the gaseous products over a heated catalyst: CO(NH 2 ) 2     (-NH 2 ) ⟶      HNCO     (6 mol)  ⟶     C 3 H 6 N 6    +    3CO 2 Melamine is used for making melamine-formaldehyde plastics. Cyanamide itself is a tautomeric compounds (amidine system), and Raman s
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Cyanogens

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Cyanogens Cyanogen is also known as ethanedinitrile . Cyanogens may be prepared by heating the cyanides of mercury of silver. Hg(CN) 2     ⟶    (CN) 2    +   Hg Cyanogen is a poisonour, colourless gas, b.p. -21 o C, and is stable in spite of the fact that its heat of formation is +292.9 kJ mol -1 . It is hydrolysed by water, the main products being hydrocyanic acid and cyanic acid, and minor products being oxamide and ammonium formate. When cyanogens is heated at 400 o C, it polymerises to paracyanogen, which at 800 o C, regenerates cyanogens. The structure of cyanogens is probably best represented as a resonance hybrid, (I) being the most important:
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Alkil isocyanides

Alkil isocyanides This is also known as isonitriles or carbylamines. General methods of preparation 1By heating an alkyl iodide with silver cyanide in aqueous ethanolic solution; a small amount of cyanide is also formed : RI    +    AgCN     ⟶      RNC    +    AgI 2   By heating a mixture of primary amine and chloroform with ethanolic potassium hydroxide:   RNH 2    +    CHCl 3    +    3KOH     ⟶      RNC    +    3KCl    +    3H 2 O 3 Dehydration of N-substituted formamides with phosphoryl chloride in pyridine produces isocyanides. RNHCHO      (POCl 3 )  ⟶     RNC General properties The alkyl isocyanides are poisonous, most unpleasant-smelling liquids, with lower boiling points than the isomeric cyanides. They are not very soluble in water, the nitrogen atom not having a lone pair of electrons available for hydrogen bonding. Alkyl isocyanides absorb in the region 2185-2120 cm -1 . Reaction 1.  Allkyl isocyanides are hydrolysed to an amine and form
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Alkyl cyanide

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Alkyl cyanide Alkyl cyanides are also known as nitriles or carbonitriles. Nomenclature This group of compounds is usually named either as the lakyl cyanides ( i.e ., the lakyl derivatives of hydrogen cyanide), or as the nitrile of the acid which is produced on hydrolysis, the suffix –ic of the trivial name being replaced by -onitrile , e.g . HCN                             hydrogen cyanide or formonitrile CH 3 CN                         methyl cyanide or acetonitrile (CH 3 ) 2 CHCN               isopropylcyanide or isobutyronitrile General methods of preparation 1. By the dehydration of acid amides with phosphorus pentoxide. High molecular weight acid amides are dehydrated to the corresponding cyanide by heat alone. Cyanides are prepared industrially by passing a mixture of carboxylic acid and ammonia over alumina at  500 o C . This reaction probably occurs as follows: RCO 2 H   +   NH 3     ⟶    RCO 2 NH 4    (Al 2 O 3 ) ⟶     H 2 O   +   RCONH 2    (Al 2
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