Which among the following is strongest base in gas phase ?

Question

Accepted Answer

Triethylamine is the strongest base in the gas phase among the given options. Here's a detailed explanation supporting this:

1. **Triethylamine (Option 1):** Triethylamine is a tertiary amine with three ethyl groups attached to the nitrogen atom. In the gas phase, the basicity of an amine is largely determined by the availability of the lone pair of electrons on the nitrogen atom for protonation. The ethyl groups in triethylamine are electron-donating due to the inductive effect, which increases the electron density on the nitrogen atom, making it more available to accept a proton. Additionally, in the gas phase, there are no solvent effects to stabilize the protonated form, so the intrinsic electron-donating ability of the ethyl groups makes triethylamine a very strong base.

2. **Diethylamine (Option 2):** Diethylamine is a secondary amine with two ethyl groups. While it also benefits from the electron-donating effect of the ethyl groups, it is less sterically hindered than triethylamine. However, in the gas phase, the steric hindrance is less of a factor compared to the electron-donating ability, and triethylamine's three ethyl groups provide a greater electron-donating effect than the two in diethylamine.

3. **Ethylamine (Option 3):** Ethylamine is a primary amine with only one ethyl group. While it is a stronger base than ammonia due to the electron-donating effect of the ethyl group, it is not as strong as triethylamine, which has three ethyl groups enhancing the electron density on the nitrogen atom.

4. **Ammonia (Option 4):** Ammonia is the simplest amine with no alkyl groups. It has a lone pair of electrons on the nitrogen atom, but without any electron-donating alkyl groups, its basicity is lower compared to the other amines listed. In the gas phase, ammonia is the weakest base among the options provided.

In summary, triethylamine's strong basicity in the gas phase is due to the cumulative electron-donating effect of its three ethyl groups, which significantly increases the electron density on the nitrogen atom, making it the strongest base among the given options.