Final answer:
The difference in basicity between ethyl and methyl substituted amines can be attributed to the presence of alkyl groups and their electron-releasing abilities. In ethyl substituted amines, secondary amines are more basic than tertiary amines due to the larger dimensions and lower electron-releasing ability of ethyl groups compared to methyl groups.
Step-by-step explanation:
The discrepancy in the basic strength order of ethyl substituted amines and methyl substituted amines is due to the nature of the alkyl groups attached to the nitrogen atom. In the case of ethyl substituted amines, the order is CX₂HX₅>X₂NH>CX₂HX₅>NHX₃, with secondary amines being more basic than tertiary, followed by primary and then ammonia.
However, in methyl substituted amines, the order is CHX₃>X₃N>NHX₃, with tertiary amines being less basic than primary amines.
The difference in basicity is attributed to the presence of alkyl groups. In ethyl substituted amines, all the alkyl groups are ethyl, which have larger dimensions and lower electron-releasing ability compared to methyl groups. As a result, the lone pair on the nitrogen atom in secondary amines is more available for donation, making them more basic than tertiary amines.