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Chapter 6 Suggested solutions for Chapter 6 33 Problem 7 Each of these compounds is a hemiacetal and therefore formed from an alcohol and a carbonyl compound. In each case give the structure of these original materials. 0 MeO Me OH oH OH Purpose of the problem To give you practice in seeing the underlying structure of a hemiacetal. Suggested solution Each OH group represents a carbonyl group in disguise (marked with a black blob). Just remove the other oxygen atom with whatever is attached to it and you have the two components: an alcohol and an aldehyde or a ketone. The first example shows how it is done. break this bond 0 oH oH 0 0 = Ho H The next is similar but the alcohol is from a different molecule. 0 0 + Do not be deceived by the next: it is not symmetrical. There is one hemiacetal (two oxygens on the same carbon atom) but the other end of the molecule is a simple tertiary alcohol. 0 MeO Me MeOH + Me OH tertiary alcohol oH not a hemiacetal Similarly, the last two examples are not quite the same. The first is indeed symmetrical but the second has one oxygen atom in a different position. There is only one hemiacetal. OH OH 0 + + 0 0 H H OH OH 0 OH + 0 0 H secondary alcohol not a hemiacetal