Compounds having the structure R2C(OR')2 ( R' ≠ H ) and thus diethers of geminal diols. Originally, the term was confined to derivatives of aldehydes (one R = H), but it now applies equally to derivatives of ketones (neither R = H ). Mixed acetals have different R' groups., germinaalsete dioolide dieetrid üldvalemiga R2C(OR')2 ( R' ≠ H )