What is the multiplicity of the methylene hydrogens indicated in the proton NMR of the following compound? CH3CH2OCH_CHOCH2CH3 Help Save Multiple Choice
a. singlet
b. doublet
c. triplet
d. quartet
The Correct Answer and Explanation is :
The correct answer is (c) triplet.
Let’s break down the structure and reasoning:
The compound given is CH3CH2OCH_CHOCH2CH3. This is an ether, specifically ethoxyethanol, and it contains different environments for hydrogen atoms that will produce distinct signals in the proton NMR spectrum.
- Methylene hydrogens (CH2):
There are two CH2 groups in the compound. The first CH2 group is attached to the oxygen (O) and is in the -CH2O group, while the second CH2 group is part of the -CH2CH3 group at the end. - Coupling with Neighboring Hydrogens:
- The CH2 group attached to the oxygen (in -CH2O) will couple with the neighboring hydrogens on the adjacent CH3 group. This results in a triplet (three peaks), which occurs due to the splitting caused by the three equivalent hydrogens in the neighboring CH3 group.
- Similarly, the second CH2 group (in the CH2CH3 chain) will also couple with the neighboring CH3 group, producing a triplet as well. The splitting occurs due to the three equivalent hydrogens in the neighboring CH3 group.
Thus, for the methylene hydrogens in this case (the CH2 groups), the multiplicity observed would be a triplet. This is because each of the methylene groups is coupled with three equivalent hydrogens from the adjacent methyl groups (CH3), causing the signal to split into three peaks, which is characteristic of a triplet in proton NMR.
Key Points:
- The multiplicity of a signal in proton NMR depends on the number of adjacent hydrogens (coupling protons).
- A triplet indicates three equivalent protons in the adjacent group.