Consider the isomers of hydrocarbon with molecular formula C_5H_ 10 . These isomers do not decolourise KMnO_4 solution. These isomers are subjected to chlorination with chlorine in presence of light to give monochloro compounds. The total number of monochloro compounds (structural isomers only) formed is _______.
A. A
The hydrocarbon with molecular formula C_5H_ 10 has a degree of unsaturation of 1. Since its isomers do not decolourise KMnO_4 solution, they do not contain any carbon-carbon double bonds. Thus, they must be cycloalkanes. The possible structural isomers of cyclic C_5H_ 10 and the number of their monochloro structural isomers are as follows: 1. Cyclopentane: All carbon atoms are equivalent. Chlorination gives 1 monochloro product (chlorocyclopentane). 2. Methylcyclobutane: There are 4 different types of hydrogen atoms (on the methyl group, on C_1, on C_2/C_4, and on C_3). Chlorination gives 4 monochloro products. 3. Ethylcyclopropane: There are 4 different types of hydrogen atoms (on the CH_3 of ethyl, on the CH_2 of ethyl, on C_1 of the ring, and on C_2/C_3 of the ring). Chlorination gives 4 monochloro products. 4. 1,1-Dimethylcyclopropane: There are 2 different types of hydrogen atoms (on the two equivalent methyl groups, and on the two equivalent CH_2 groups of the ring). Chlorination gives 2 monochloro products. 5. 1,2-Dimethylcyclopropane: There are 3 different types of hydrogen atoms (on the two equivalent methyl groups, on the two equivalent CH groups of the ring, and on the CH_2 group of the ring). Chlorination gives 3 monochloro products. Since each of these cycloalkanes has a different carbon skeleton, their monochloro derivatives will all be distinct structural isomers. Total number of monochloro compounds (structural isomers only) = 1 + 4 + 4 + 2 + 3 = 14. Answer: 14
Related: Chemistry — Hydrocarbons · All PYQ Banks