The correct order of basic strength of ethylamine, diethylamine, and triethylamine in chlorobenzene is:

Step-by-step solution

Chlorobenzene is a non-polar, aprotic solvent. In non-polar solvents or in the gas phase, the basic strength of amines is determined solely by the +I (inductive) effect of the alkyl groups, as there is no solvation effect (hydrogen bonding) to stabilize the conjugate acid. The +I effect increases with the number of alkyl groups attached to the nitrogen atom, which increases the electron density on the nitrogen atom and its ability to donate the lone pair. Therefore, the basic strength increases in the order: primar