Question

What will be type of proton NMR spectrum of 2.2.-dimethylpropane

• A. Quartet
• B. Doublet
• C. Triplet
• D. Singlet

Answer 1

The Correct Option is D

To determine the type of proton NMR spectrum for 2,2-dimethylpropane, we need to analyze its structure and the environment of its hydrogen atoms.

Structure of 2,2-dimethylpropane:

2,2-dimethylpropane is a branched alkane with the chemical formula \( \text{(CH}_3\text{)}_4\text{C} \). 

Analysis of Hydrogen Environments:

• The molecule consists of a central carbon atom bonded to four identical methyl groups (\( \text{C(CH}_3\text{)}_4 \)).
• All the hydrogen atoms in the molecule are equivalent because they are all part of methyl groups bonded to the same central carbon atom. Therefore, there is only one unique hydrogen environment.

Type of NMR Spectrum:

In proton NMR, the splitting pattern of signals is determined by the number of neighboring nonequivalent hydrogen atoms causing spin-spin coupling. Since all hydrogens in 2,2-dimethylpropane are equivalent, no coupling occurs, resulting in a single peak.

Conclusion:

• The NMR spectrum of 2,2-dimethylpropane will show a single peak because there is only one set of equivalent hydrogen atoms and no neighboring hydrogens for spin coupling.
• Hence, the type of the proton NMR spectrum is a singlet.