Barbiturates imide group

Figure 4.4 The imide group and resonance stabilisation of barbiturate anions.

Barbiturates are central nervous system depressants used as hypnotic drugs and anesthetics. They are all derivatives of barbituric acid (R=R =H), which has no sedative properties. It is called an acid because the carbonyl groups render the imide hydrogens acidic ... 

Phenytoin is an anticonvulsant widely used in the treatment of epilepsy The properties of phenytoin resemble those of barbiturates. It is a cyclic imide with a pKa of 8.3. The anion is stabilised by resonance of the negative charge onto the oxygens of the carbonyl group and the drug is usually administered as the sodium salt to increase water solubility See Figure 3.15. 

Barbiturates, hydantoins, and imides contain functional groups related to amides but tend to be more reactive. Barbituric acids such as barbital, phenobarbital, amobarbital, and metharbital undergo ring-opening hydrolysis, as shown in Scheme 15.80-81 Decomposition products formed from these drug substances are susceptible to further decomposition reactions such as decarboxylation. The hydrolysis rates of these substances depend on the substituents Ri, R2, and R3. For some allylbarbituric acids, the effects of these substituents on hydrolysis rates can be explained in terms of Hammett s o value.82... 

R Organic acids, alcohols, phenols, ketones, esters, ethers, amides, imines, imides, nitriles, aromatic amines, sulfonamides, barbiturates, aromatic hydrocarbons, other miscellaneous groups. Regression equations for calculation of from Kw in any of 20 different solvent/water systems are given. Equations primarily for mono-functional chemical classes. 

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