(CH3)3C- is t-butyl group.

CH3CH2CH2CH2- is n-butyl group.

Butyl is not a compound but is part of a compound. Butyl simply means a 4 carbon chain, as in butyl alcohol, which is CH3CH2CH2CH2OH. This is a compound.

If u are referring to the carbocations of n-butyl, sec-butyl, and t-butyl, the most stable is the one that has the most alkyl groups attached to the positively charged carbon atom. In this case:

- n-butyl has only 1 alkyl group attached

- sec-butyl has 2 alkyl groups attached

- t-butyl has 3 alkyl groups attached

Therefore, t-butyl is the most stable carbocation

Butyl Rubber Market

Amyl nitrite, sodium nitrite, sodium thiosulfate