Q18P Predict the theoretical number o... [FREE SOLUTION]

Chapter 13: Q18P (page 675)

Predict the theoretical number of different NMR signals produced by each compound and give approximate chemical shifts. Point out any diastereotopic relationships.
2-bromobutane
Cyclopentanol
Ph-CHBr-CH₂Br
Vinyl chloride

Short Answer

Expert verified

This compound shows five NMR signals. H_Cand H_Dare diastereotopic. a = 未 1.5, b = 未 3.6, c, d = 未 1.7, e = 未 1.0
This compound shows six NMR signals. H_C and H_D are diastereotopic. Also, H_E and H_F are diastereotopic.a = 未 2.5, b = 未 3.9, c, d = 未 1.6, e, f = 未 1.3
This compound shows six NMR signals. H_E and H_F are diastereotopic. a, b, c = 未 7.2, d = 未 5.0, e, f = 未 3.6
This compound shows three NMR signals. H_A and H_B are diastereotopic. a, b = 未 5-6, c = 未 7-8

Step by step solution

Step-1. Explanation of part (a):

2-bromobutane shows five NMR signals. It has five different kinds of protons. Diastereotopic protons are chemically non-equivalent protons and they have different chemical shifts. This type of proton is usually found in chiral molecule. Compound should not possess any plane of symmetry. Also, if after passing plane through protons, if protons get bisected, then also, protons will be diastereotopic. H_Cand H_Dare diastereotopic in 2-bromobutane.

The chemical shift values of protons showing NMR signals are, a = 未 1.5, b = 未 3.6, c, d = 未 1.7, e = 未 1.0

2-bromobutane

Step-2. Explanation of part (b):

Cyclopentanol shows six NMR signals. It has six different kinds of protons. Diastereotopic protons are chemically non-equivalent protons and they have different chemical shifts. This type of proton is usually found in chiral molecule. Also, if after passing plane through protons, if protons get bisected, then also, protons will be diastereotopic. H_C and H_Dare diastereotopic. Also, H_Eand H_Fare diastereotopic.

The chemical shift values of protons of cyclopentanol are, a = 未 2.5, b = 未 3.9, c, d = 未 1.6, e, f = 未 1.3

Cyclopentanol

Step-3. Explanation of part (c):

This compound shows six NMR signals. It has six different kinds of protons. Diastereotopic protons are chemically non-equivalent protons and they have different chemical shifts. This type of proton is usually found in chiral molecule. Also, if after passing plane through protons, if protons get bisected, then also, protons will be diastereotopic. H_E and H_F are diastereotopic.

The chemical shift values of protons are, a, b, c = 未 7.2, d = 未 5.0, e, f = 未 3.6

Six different types of protons in a compound

Step-4. Explanation of part (d):

Vinyl chloride shows three NMR signals. It has three different kinds of protons. Diastereotopic protons are chemically non-equivalent protons and they have different chemical shifts. This type of proton is usually found in chiral molecule. Compound should not possess any plane of symmetry. Also, if after passing plane through protons, if protons get bisected, then also, protons will be diastereotopic. H_Aand H_Bare diastereotopic.

The chemical shift values of protons in vinyl chloride are a, b = 未 5-6, c = 未 7-8