Hydrolysis orthoformic acid trimethyl ester

Fig. 9.13. Mechanism of the acid-catalyzed hydrolysis of orthoformic acid trimethyl ester.

One can also acetalize carbonyl compounds completely without using the alcohol in excess. This is the case when one prepares dimethyl or diethyl acetals from carbonyl compounds with the help of the orthoformic acid esters trimethyl orthoformate HC(OCH3)3 or triethyl orthoformate HC(OC2H5)3, respectively. In order to understand these reactions, one must first clearly understand the mechanism for the hydrolysis of an orthoester to a normal ester (Figure 7.16). It corresponds step by step to the mechanism of hydrolysis of <9,<9-acctals, which was detailed in Figure 7.15. The fact that the individual steps are really strictly analogous becomes very clear when one takes successive looks at... 

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