Why does tert-Butyl methyl ether #[CH_3OC(CH_3)_3]# exhibits two NMR signals?

1 Answer
Oct 28, 2014

The H NMR spectrum of t-butyl methyl ether exhibits two signals because the methyl groups are in two different chemical environments.


Three of the CH₃ groups are attached to the same carbon, so they are all in the same chemical environment. They are all equivalent.

The remaining CH₃ group is attached to an O atom, so it is in a different chemical environment.

We should see two signals with area ratios 9:3 or 3:1.

The electronegative O atom pulls all signals downfield. The effect decreases rapidly with distance.

The CH₃ group on the O atom is pulled about 2.3 ppm downfield from its normal value of δ 0.9. We should see a 3H signal at about δ 3.2.

The CH₃ groups of the t-butyl group are pulled about 0.3 ppm downfield. We should see a 9H signal at about δ 1.2.