Question #84373

organic compound has molecular formula CH,,(A). A on heating with soda lime yields a hydrocarbon BCH) Bonblorination yields a single isomeric alkyl chloride C(CH.CI). Deduce the structures of A, B and C

Expert's answer

organic compound has molecular formula CH11(A)\mathrm{CH}_{11}(\mathrm{A}). A on heating with soda lime yields a hydrocarbon BCH) Bonblorination yields a single isomeric alkyl chloride C(CH.Cl). Deduce the structures of A, B and C

**Solution.** We will proceed from two cases, because it is not entirely clear what is meant by the expression "the only isomeric alkyl chloride".

1) We understand this expression in such a way that one alkyl chloride is formed during chlorination. Then B is methane (CH4)(\mathrm{CH}_4). When chlorination is the reaction: CH4+Cl2=CH3Cl+HCl\mathrm{CH}_4 + \mathrm{Cl}_2 = \mathrm{CH}_3\mathrm{Cl} + \mathrm{HCl}. Then substance C is chloromethane (CH3Cl)(\mathrm{CH}_3\mathrm{Cl}). Since substance A initially reacts with soda lime, then A is acetic acid (CH3COOH)(\mathrm{CH}_3\mathrm{COOH}), and reaction: CH3COOH+NaOH=NaHCO3+CH4\mathrm{CH}_3\mathrm{COOH} + \mathrm{NaOH} = \mathrm{NaHCO}_3 + \mathrm{CH}_4.

2) We understand this expression as the formation of two isomeric chlorinated alkanes, that is, one chlorinated alkane has one single isomer. Then B is 2-methylpropane. Then the chlorination reaction will go in two ways:


H3CCH(CH3)CH3+Cl2=H3CC(Cl)(CH3)CH3 (2-chloro-2-methylpropane)+HCl;\mathrm{H}_3\mathrm{C}-\mathrm{CH}(\mathrm{CH}_3)-\mathrm{CH}_3 + \mathrm{Cl}_2 = \mathrm{H}_3\mathrm{C}-\mathrm{C}(\mathrm{Cl})(\mathrm{CH}_3)-\mathrm{CH}_3 \text{ (2-chloro-2-methylpropane)} + \mathrm{HCl};H3CCH(CH3)CH3+Cl2=H3CCH(CH3)CH2Cl (1-chloro-2-methylpropane)+HCl. Then substance C can be either chloralkane from the first reaction or chloralkan from the second reaction.\mathrm{H}_3\mathrm{C}-\mathrm{CH}(\mathrm{CH}_3)-\mathrm{CH}_3 + \mathrm{Cl}_2 = \mathrm{H}_3\mathrm{C}-\mathrm{CH}(\mathrm{CH}_3)-\mathrm{CH}_2\mathrm{Cl} \text{ (1-chloro-2-methylpropane)} + \mathrm{HCl}. \text{ Then substance C can be either chloralkane from the first reaction or chloralkan from the second reaction.}


Substance A will then have the formula: H3CCH(CH3)CH2COOH\mathrm{H}_3\mathrm{C}-\mathrm{CH}(\mathrm{CH}_3)-\mathrm{CH}_2-\mathrm{COOH} (3-methylbutanoic acid), and reaction with soda lime: H3CCH(CH3)CH2COOH+NaOH=NaHCO3+H3CCH(CH3)CH3\mathrm{H}_3\mathrm{C}-\mathrm{CH}(\mathrm{CH}_3)-\mathrm{CH}_2-\mathrm{COOH} + \mathrm{NaOH} = \mathrm{NaHCO}_3 + \mathrm{H}_3\mathrm{C}-\mathrm{CH}(\mathrm{CH}_3)-\mathrm{CH}_3.

**Answer:** 1) A – acetic acid (CH3COOH)(\mathrm{CH}_3\mathrm{COOH}), B – methane (CH4)(\mathrm{CH}_4), C – chloromethane (CH3Cl)(\mathrm{CH}_3\mathrm{Cl});

2) A – 3-methylbutanoic acid (H3CCH(CH3)CH2COOH)(\mathrm{H}_3\mathrm{C}-\mathrm{CH}(\mathrm{CH}_3)-\mathrm{CH}_2-\mathrm{COOH}), B – 2-methylpropane (H3CCH(CH3)CH3)(\mathrm{H}_3\mathrm{C}-\mathrm{CH}(\mathrm{CH}_3)-\mathrm{CH}_3), C – H3CC(Cl)(CH3)CH3\mathrm{H}_3\mathrm{C}-\mathrm{C}(\mathrm{Cl})(\mathrm{CH}_3)-\mathrm{CH}_3 (2-chloro-2-methylpropane) or H3CCH(CH3)CH2Cl\mathrm{H}_3\mathrm{C}-\mathrm{CH}(\mathrm{CH}_3)-\mathrm{CH}_2\mathrm{Cl} (1-chloro-2-methylpropane).

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