Consider the following reactions. For parts \(\mathrm{b}-\mathrm{d}\), see Exercise \(62 .\) a. When \(\mathrm{C}_{5} \mathrm{H}_{12}\) is reacted with \(\mathrm{Cl}_{2}(g)\) in the presence of ultraviolet light, four different monochlorination products form. What is the structure of \(\mathrm{C}_{5} \mathrm{H}_{12}\) in this reaction? b. When \(\mathrm{C}_{4} \mathrm{H}_{8}\) is reacted with \(\mathrm{H}_{2} \mathrm{O}\), a tertiary alcohol is produced as the major product. What is the structure of \(\mathrm{C}_{4} \mathrm{H}_{8}\) in this reaction? c. When \(\mathrm{C}_{7} \mathrm{H}_{12}\) is reacted with \(\mathrm{HCl}\), 1 -chloro-1-methylcyclohexane is produced as the major product. What are the two possible structures for \(\mathrm{C}_{7} \mathrm{H}_{12}\) in this reaction? d. When a hydrocarbon is reacted with \(\mathrm{H}_{2} \mathrm{O}\) and the major product of this reaction is then oxidized, acetone (2-propanone) is produced. What is the structure of the hydrocarbon in this reaction? e. When \(\mathrm{C}_{5} \mathrm{H}_{12} \mathrm{O}\) is oxidized, a carboxylic acid is produced. What are the possible structures for \(\mathrm{C}_{5} \mathrm{H}_{12} \mathrm{O}\) in this reaction?

Step by step solution

01

Reaction of C5H12 with Cl2 in the presence of Ultraviolet light

C5H12 is a saturated alkane with a molecular formula of CnH2n+2. With five carbon atoms, this compound is pentane. There are no other structural isomers for C5H12 besides pentane itself. The structure of C5H12 in this reaction is: H3C-CH2-CH2-CH2-CH3. b. Determine the structure of C4H8 when it reacts with H2O to produce a tertiary alcohol

02

Reaction of C4H8 with H2O

C4H8 is an alkene with a molecular formula of CnH2n. In this reaction, a tertiary alcohol is formed. This indicates that an elimination process must occur at a tertiary carbon. The structure of C4H8 in this reaction is 2-methylpropene (isobutylene). The structure of C4H8 in this reaction is: H2C=C(CH3)2. c. Identify two possible structures for C7H12 when it reacts with HCl and produces 1-chloro-1-methylcyclohexane

03

Reaction of C7H12 with HCl

C7H12 is a seven-carbon alkene (CnH2n) that reacts with HCl to form 1-chloro-1-methylcyclohexane as the major product. The two possible structures for C7H12 that could lead to this product are 1-methylcyclohexene and 3-methylcyclohexene. The two possible structures for the reaction are: 1. 1-methylcyclohexene: Ch3C1 of HCl adds to the double bond on position 1 of the cyclohexene producing 1-chloro-1-methylcyclohexane. 2. 3-methylcyclohexene: H atom of HCl adds to the double bond on position 3 of the cyclohexene leading to a carbocation on position 1 and followed by addition of chlorine producing 1-chloro-1-methylcyclohexane. d. Determine the structure of the hydrocarbon when it reacts with H2O and the major product is oxidized to acetone

04

Reaction of hydrocarbon with H2O followed by oxidation to acetone

Acetone has a molecular formula of C3H6O. If the major product of the reaction between the hydrocarbon and H2O is then oxidized to acetone, we deduce that the initial hydrocarbon contains four carbon atoms (C4H8). Since a double bond is present, the possible hydrocarbon structure is that of an alkene. The structure of the hydrocarbon in this reaction is 2-methylpropene (isobutylene) as H2O adds across the double bond and oxidized later to 2-propanone (acetone). The structure of the hydrocarbon in this reaction is: H2C=C(CH3)2. e. Identify possible structures for C5H12O, which upon oxidation produces a carboxylic acid

05

Oxidation of C5H12O to carboxylic acid

C5H12O is a five-carbon alcohol. Alcohols can be oxidized to aldehydes, ketones, or carboxylic acids. In this case, oxidation generates a carboxylic acid. The possible structures of C5H12O that would be oxidized to carboxylic acids are: 1. 1-pentanol: Upon oxidation, this primary alcohol is converted into pentanoic acid. The structure of 1-pentanol is: H3C-CH2-CH2-CH2-CH2-OH. 2. Pentan-2-ol: Upon oxidation, this secondary alcohol is converted to pentanoic acid. The structure of pentan-2-ol is: H3C-CH2-CH(OH)-CH2-CH3.

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