Question 15.6: Writing the Products Obtained from Acetal hydrolysis Write t...
Writing the Products Obtained from Acetal hydrolysis
Write the structure of the aldehyde or ketone that forms by hydrolysis of the following acetal:
\begin{matrix}\qquad \qquad\,\,\,\,\,\,\, OCH_2CH_3 \\ CH_3\underset{|}{C}HCH_2\underset{|}{\overset{|}{C}}OCH_2CH_3 \\ CH_3 \,\,\,\,\,\,\,\,\,\,H \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\end{matrix}+H_2O \stackrel{\text{Acid}}{\longrightarrow}?
ANALYSiS The products are the aldehyde or ketone plus two molecules of the alcohol from which the acetal could have been formed. First, identify the two C—O acetal bonds, redrawing the structure if necessary.
Next, break the H—OH bond and one of the acetal C—OR bonds (in this case, it does not matter which one); move the water OH to the acetal carbon to form the hemiacetal and the water H to the OR to form one molecule of HOR.
Remove the H and OR groups from the hemiacetal, and change the C—O single bond to a C=O double bond to give carbon the four bonds it must have. Combine the H and OR you removed from the second alcohol molecule.
In this example, the product is an aldehyde. The procedure is identical if you start with a ketal rather than an acetal.