Isopropylbarbituric acid

Any untransformed isopropylbarbituric acid is recovered from the filtrate after separating out the unchanged dibrompropylene, by precipitation with concentrated hydrochloric acid. 

Proprietary Name. Alurate 5-Allyl-5-isopropylbarbituric acid... 

Disposition in the Body. Metabolised by side-chain oxidation to 5-(2-acetonyl)-5-isopropylbarbituric acid. About 6 to 16% of a dose is slowly excreted in the urine as the metabolite with about 1 to 3% as unchanged drug the metabolite is still detectable in urine 9 days after a single dose. 

Baibiturates with an intermediate duration of action are used principally as sedative-hypnotics. They include Amobarbl-tal, USP, S-ethyl-S-isopentylbaibituric acid (Amytal), anil its water-soluble sodium salt. Amobarbital Sodium, USP, S-allyl-S-isopropylbarbituric acid (aprobarbital. Alunne) Butabarbitd Sodium, USP, the water-soluble sodium sail of S-sec-butyl-S-ethylbarbituric acid (Butisol Sodium). 

Equations (10) and (11) can also be expressed in exponential form, as well as in forms which use AG as the dependent variable rather than pK (from the van t Hoff isotherm, AG = -RT In K). For equilibrium reactions in aqueous and other polar solutions, the ACp value is expected to have a finite value, due to the significant changes in solvent structure which occur when ionization takes place. For some compoimds, the ACp value may have a large uncertainty and be not statistically different to zero, depending on the precision of the raw data (e.g., 5,5-di-isopropylbarbituric acid) [89]. In these cases, the pRa temperature dependence is satisfactorily described by the integrated van t Hoff equation [Eq. (10) without the C log T term]. This equation will give a linear van t Hoff plot of pfCg versus 1/T. 

The potentiometric determination of ttie "proton lost" dissociation constant of six N-mettiylated barbiturates was carried out. The constants are tabulated as association constants 1 311 for an ionic strength mu = 0.10 and t = 20.0 °C. The influence of substituents at N1 and C5 on the acid strengfli is discussed. From ttie determination of ttie "proton gained" dissociation constants in strongly acid medium it could not be concluded how many protons can be bound. The 6 barbiturates studied were 1-methyl-5,5-dipropyl- l,5-dimethyl-5-isopropyl- l,5-dimethyl-5-ethyl- l-mettiyl-5-ettiyl-5-butyl- l-mettiyl-5,5-diallyl- and l-methyl-5-propyl-5-isopropylbarbituric acid."... 

NB By extrapolation of apparent values to 0% 7-(2-hydroxypropyl)-theophylline that was used as a complexing agent to increase solubility. TRIS was used as a pKg reference (pKa = 8.18 at 20 C). See also Ritschel, who cited Fincher JH, Entrekin DN, Hartman CW, Surfactant-Base-Barbiturate Suppositories I Rectal absorption in rabbits, J. Pharm. Sci., 55,23-28 (1966). Fincher in turn cited values from Shanker LS, Absorption of drugs from the rat colon, JPET, 126,283-290 (1959) for 4 cpds 5-allyl-5-isobutylbarbituric acid (7.86) 5-butyl-5-ethylbarbituric acid (8.10) 5-efhyl-5-(l-mefiiylbutyl)barbituric acid (8.17) and 5-allyl-5-isopropylbarbituric acid (7.54). 

International Union of Pure and Applied Chemistry (lUPAC), 2, 7,15, 27 Ionic activity coefficient, 8 Ionic strength, 10-11,14, 21-22 pJCa values and, 6 Isonicotinic add, 5,12 5,5-di-isopropylbarbituric acid, 17 lUPAC pJCa compilations, 2-4... 

Ethyl-5-isopropylbarbituric acid a-Etbyl- -metbylbutyrylurea in aq. NHg beated 5-10 min. at 200° in a stainless steel rocking bomb Y 91.8% a-etbyl-j -metbylbutyramide. Y 93.5%... 

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