How many signals would you expect to find in the 'H nmr spectrum of each of the following compounds?
c. 1, 4-dibromobutane
d. 2, 2, 3, 3-tetrabromobutane
Describe the appearance of the^1H nmr spectrum of each of the following compounds. How many signals would you expect to find and into how many peaks will each signal be split?
a. 1, 2-dichloroethan
b. 1, 1, 1-trichloroethane
c. 1, 1, 2-trichloroethane
d. 1, 2, 2-trichloropropane
e. 1, 1, 1, 2-tetrachlorpropane
Proton NMR spectroscopy
H NMR is a valuable analytical tool that is often used in organic chemistry for the study of the composition and structure of unknown organic molecules.
The movement of the peaks (chemical shift) is determined by the chemical environment of the protons, while the integration of the peaks relate to the number of protons that each signal represent.
The proximity of different types of protons to each other can be seen in the coupling of signals (multiplicity) of the peaks.
Answer and Explanation:
1. The first step is to draw the structure and then it is easy to identify similar protons. There will be one signal for each set of similar protons.
On the image below, the similar protons have been allocated in each structure using the same letter.
a. 1-buantol - 5 Signals (although some of these signals may overlap)
b. butane - 2 Signals
c. 1, 4-dibromobutane -2 Signals
d. 2, 2, 3, 3-tetrabromobutane -1 Signal
2. The first step is to draw the structures - see image below.
From the structures the location of the protons can be seen and the coupling on the H NMR can be predicted. The image below contains the explanation for the answers
a. 1, 2-dichloroethan - 1 Signal; Triplet
b. 1, 1, 1-trichloroethane - 1 Signal; Singlet
c. 1, 1, 2-trichloroethane - 2 Signals; Triplet and a doublet
d. 1, 2, 2-trichloropropane - 2 Signals; Singlets
e. 1, 1, 1, 2-tetrachlorpropane 2 Signals; Doublet
Learn more about this topic:
from Organic Chemistry: Help & ReviewChapter 2 / Lesson 2