The crystal structure of polymorph IV of 5,5-diethylbarbituric acid (barbital)

Hydrogen bonding NH...O = C of barbiturates: the (1:1) crystal complex of urea and 5,5-diethylbarbituric acid (barbital)

“…Crystal structure (a) Barbituric acids 5,5-Diethylbarbituric acid (barbital), form I (Craven, Vizzini & Rodrigues, 1969) Barbital, form II (Craven, Vizzini & Rodrigues, 1969) Barbital, form IV (Craven & Vizzini, 1971) 5-Ethyl-5-isoamylbarbituric acid (amobarbital), form I 2-89 Amobarbital, form II 2.91, 2.86 5-Ethyl-5-(3,3-dimethylbutyl)barbitutic acid (Gartland & Craven, 1971) 2.82 5-Ethyl-5-(1-methylbutenyl)barbituric acid (Craven & Cusatis, 1969) 2.87, 2.92 5-Ethyl-5-butylbarbituric acid (Bideau, 1971) 2.86 5-Ethyl-5-(1-cyclohexen-l-yl)barbituric acid (Bideau & Artaud, 1970) 2.87 5-Ethyl-5-(1-cyciohepten-l-yl)barbituric acid (Bideau, Leroy & Housty, 1969) 2"89, 2.87 5-Ethyl-5-phenylbarbituric acid, form III (Williams, 1974) 2.89, 2-91 5-Methyl-5-phenylbarbituric acid (Bravic, Housty & Bideau, 1968) 2.90 5-Ethylbarbituric acid (Gatehouse & Craven, 1971) 2.85 (b) 1-Methylbarbituric acids 1-Methyl-5,5-diethylbarbituric acid (Wunderlich, 1973) 2"84 1-Methyl-5-ethyl-5-(l-cyclohexen-l-yl)barbituric acid (Bideau, Leroy & Housty, 1970) 2"88 1-Methyl-5-ethyl-5-phenylbarbituric acid (Bideau, Marly & Housty, 1969) 2.89 (c) Barbiturate anions Sodium barbital (Berking & Craven, 1971) 2.84 Calcium barbital trihydrate (Berking, 1972) Guanidinium barbital dihydrate (McClure & Craven, 1973) (Craven & Gartland, 1970) 2.98, 2.94, 2.93 -5,5-Diethylbarbituric acid/aminopyrine (1 : 1) (Kiryu, 1971) 2.82 2"75 5,5-Diethylbarbituric acid/urea (1:1) (This paper) -2.78, 2-80 5,5-Diethylbarbituric acid/acetamide) (1:1) (Hsu & Craven, 1974a) -2"82, 2-82 5-Ethyl-5-isoamylbarbituric acid/salicylamide (1 : 1) (Hsu & Craven, 1974b) 2.92 -5,5-Diethylbarbituric acid/imidazole (1:1) (Hsu & Craven, 1974c) 2.91 - The shortest reported distances which we could find were 2-55/~ in cysteylglycine sodium iodide (Dyer, 1951) and 2.621~ in guanine hydrochloride monohydrate (Broomhead, 1951). Since these structure determinations were based only on zonal X-ray intensity data, a more reliable lower limit for N...O distances might be 2.67 A which occurs in the urea/ parabanic acid complex …”

Polymorphism of phenobarbitone: the crystal structure of 5-ethyl-5-phenylbarbituric acid monohydrate

“…Singh, 1965;Bolton, 1963;Craven, Vizzini & Rodrigues, 1969;Craven & Vizzini, 1969) have revealed a variety of intermolecular hydrogen-bonding schemes, and it has been shown, for example, in barbital (5,5-diethylbarbituric acid) Vizzini & Rodrigues, 1969;Craven & Vizzini, 1971) phenobarbitone suggested this compound as a subject for detailed study in the expectation that a wide variety of hydrogen-bonding schemes would be encountered.…”

Crystal Polymorphs of Barbital: News about a Classic Polymorphic System

“…6,7,11 A special preparation method was required for form IV , which transforms readily to III upon mechanical treatment. Representative diffractograms of form IV could be finally recorded from film preparations prepared on a coverslip, which then was mounted on a silicon holder.…”