Iodoform QuestionWatch this thread
I am digging in to the dim and distant past (why do exam boards expect people to know such out-dated reactions!), but seem to remember that many secondary alcohols give a positive iodoform test. This would explain why Z is positive. W is expected because it is a ketone. X is an aldehyde, but you are right, the only aldehyde that gives a positive test is ethanal. Y is a primary alcohol, so it won't give a positive test (only ethanol works).