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Chapter 18: Problem 402

One way we can explore the acidity of hydrogens with an organic molecule is to dissolve the compound in \(\mathrm{D}_{2} \mathrm{O}\) in the presence of \(\mathrm{NaOD}\). If a hydrogen is removed by the base, it will be replaced by deuterium. For example, acetaldehyde, \(\mathrm{CH}_{3} \mathrm{CHO}\), in \(\mathrm{D}_{2} \mathrm{O} / \mathrm{NaOD}\) is quickly converted to \(\mathrm{CD}_{3} \mathrm{CHO}\). What deuterio compounds would you get from each of the following compounds under those conditions? (a) acetone (c) cyclohexanone (b) ethyl alcohol (d) benzaldehyde

Short Answer

Expert verified
The deuterio compounds formed under the given conditions are: (a) Acetone: \(CH_3COCD_3\) (b) Ethyl Alcohol: \(CH_3CH_2OD\) (c) Cyclohexanone: Cyclohexanone with two alpha-deuterium atoms (d) Benzaldehyde: Benzaldehyde with an alpha-deuterium atom

Step by step solution

01

(a) Acetone

Acetone has the structure: \(CH_3COCH_3\). We need to identify the acidic hydrogen(s) that can be replaced by deuterium. The hydrogen atom attached to the carbon next to the carbonyl group of acetone is the most acidic hydrogen and can be removed by the base NaOD: \[ CH_3COCH_3 + NaOD \rightarrow CH_3COCD_3 + NaOH \]Thus, the deuterio compound formed in this case is \(CH_3COCD_3\), with all three hydrogens in the methyl group replaced by deuterium.
02

(b) Ethyl Alcohol

Ethyl alcohol has the structure: \(CH_3CH_2OH\). The acidic hydrogen is the one attached to the hydroxyl group: \[ CH_3CH_2OH + NaOD \rightarrow CH_3CH_2OD + NaOH \]The deuterio compound formed in this case is \(CH_3CH_2OD\), with the hydrogen of the hydroxyl group replaced by deuterium.
03

(c) Cyclohexanone

Cyclohexanone has the structure: \[ \begin{array}{{>{\displaystyle}l}} \text { CH-CH2-CH2-CH2 } \\ \text { || CH-CH2 } \\ \text { O } \end{array} \]The alpha-hydrogens of cyclohexanone (attached to the carbons next to the carbonyl group) are the most acidic: \[ \begin{array}{c} \text { CH-CH2-CH2-CH2 } \\ \text { || CH-CD2 } \\ \text { O} \end{array} + NaOH \]The deuterio compound formed in this case is cyclohexanone with the two alpha-hydrogens replaced by deuterium atoms.
04

(d) Benzaldehyde

Benzaldehyde has the structure: \[ \begin{array}{{>{\displaystyle}l}} \text { PhCH } \\ \text { O } \end{array} \]where Ph represents a phenyl group. The alpha-hydrogen of benzaldehyde (attached to the carbon next to the carbonyl group) is the most acidic: \[ \begin{array}{{>{\displaystyle}l}} \text { PhCD } \\ \text { O } \end{array} + NaOH \]The deuterio compound formed in this case is benzaldehyde with the alpha-hydrogen replaced by a deuterium atom.

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Most popular questions from this chapter

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