Carbonic acid, derivatives

Problem 16.49 The following carboxylic acids are unstable and their decomposition products are shown in parentheses carbonic acid, (H0)2C=0 (C02 + H20) carbamic acid, H2NCOOH (C02 + NH3) and chlorocarbonic acid, CICOOH (C02 + HCl). Indicate how the stable compounds below are derived from one or more of these unstable acids. Name those for which a common name is not given. 

Problem 16.50 What products are formed when l mol of urea reacts with (a) l mol, (b) a second mol of methyl acetate (or acetyl chloride)  

Problem 16.51 Barbiturates are sedative-hypnotic varieties of 5,5-dialkyl substituted barbituric acids. Write the reaction for the formation of Veronal (5,5-diethylbarbituric acid) from the condensation of urea with diethylmalonic ester. [See Problem 17.11(a)]. -4 

Problem 16.53 Give the name and formula for the organic product formed from 1 mol of COCl, and 2 moles of (fl) QH5NH2, (6) C2H5OH.  

1750-1680 Strong. In Raman, weak to medinm Carbamates 1690-1620 Strong. In Raman, weak to medinm Ureas 

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By reaction of polyhydroxy compounds with a carbonic acid derivative, a series of related polymers may be produced with carbonate (—0 C0 0—) linkages, the polymers being referred to as polycarbonates. Carbonic acid, C0(0H)2, itself does not exist in the free state but by means of ester exchange Figure 20.1) (1) and phosgenation techniques (II) it is possible to produce useful products. 

Carothers also produced a number of aliphatic linear polyesters but these did not fulfil his requirements for a fibre-forming polymer which were eventually met by the polyamide, nylon 66. As a consequence the polyesters were discarded by Carothers. However, in 1941 Whinfield and Dickson working at the Calico Printers Association in England announced the discovery of a fibre from poly(ethylene terephthalate). Prompted by the success of such a polymer, Farbenfabriken Bayer initiated a programme in search of other useful polymers containing aromatic rings in the main chain. Carbonic acid derivatives were reacted with many dihydroxy compounds and one of these, bis-phenol A, produced a polymer of immediate promise. 

To reduce melt viscosity an aliphatic dicarhoxylic acid may be used to partially replace the carbonic acid derivative. Easy-flow grades with a melt flow rate of 80 are now available in order to meet the stringent flow requirements involved in compact disc production. Such an improvement in flow rate is, however, at the expense of heat distortion temperature. 

G. Reactions with Carbon Dioxide and Some Carbonic Acid Derivatives... 

Thus unsubstituted (R=H) and substituted (R = alkyl) non-stabilized diyiides 1 react with phenylisocyanate and dicyclohexylcarbodiimide (R NCX), leading to the formation of new monoylide type intermediates. These last ones react in situ with carbonyl compounds through a Wittig type reaction leading respectively to a,)8-unsaturated amides 2 and amidines 3, with a high E stereoselectivity, the double bond being di- or tri-substituted [48,49]. By a similar reactional pathway, diyiides also react with carbonic acid derivatives, with the synthesis as final products of -a,/l-unsaturated esters 4 and acids 5 [50]. 

Biotin is a growth factor for many bacteria, protozoa, plants, and probably all higher animals. In the absence of biotin, oxalacetate decarboxylation, oxalosuccinate carboxylation, a-ketoglutarate decarboxylation, malate decarboxylation, acetoacetate synthesis, citrulline synthesis, and purine and pyrimidine syntheses, are greatly depressed or absent in cells (Mil, Tl). All of these reactions require either the removal or fixation of carbon dioxide. Together with coenzyme A, biotin participates in carboxylations such as those in fatty acid and sterol syntheses. Active C02 is thought to be a carbonic acid derivative of biotin involved in these carboxylations (L10, W10). Biotin has also been involved in... 

We can think of water entering the lake in terms of a titration. A solution of alkali enters a fixed volume of acid the alkaline solution is water entering from the lake s tributary rivers, and the acid is the lake, which contains the weak acid H2CO3 (carbonic acid) deriving from atmospheric carbon dioxide. The alkali in the tributary rivers is calcium hydroxide Ca(OH)2, which enters the... 

Exchange of a functionalized ring carbon with carbonic acid derivatives 331... 

The most widely used method for the preparation of [l,2,4]triazolo[3,4-A][l,3,4]thiadiazoles 85 employs 4-amino-5-thio-4/7-[l,2,4]triazoles 83 or 4-amino[l,2,4]-triazole-5(47T)-thiones 84 as starting materials. The reaction of the triazoles 83 or 84 with carbonic acid derivatives furnishes [l,2,4]triazolo[3,4-4][l,3,4]thiadiazoles with a heteroatom substituent (N, O, S) at position 6 the O- and S-functions are formulated as 6-hydroxy and 6-thio derivatives 85a or as thiadiazol-(5/7)6-ones and -thiadiazole-(577)6-thiones 85b, respectively reaction with carboxylic acid derivatives provides the 6-substituted-[l,2,4]triazolo[3,4-4][l,3,4]-thiadiazoles 85c (Equation 20 Table 3). 

Table 3 Formation of [l,2,4]triazolo[3,4-b][l,3,4]thiadiazoles 85 from carbonic acid derivatives...

Hydrazines of type 89 react with various carbonic acid derivatives to furnish cyclized product. Under basic conditions (KOH), in the presence of carbon disulfide or arylisothiocyanates, the cyclized thione 90 is obtained (Scheme 7) <1966JOG3528, 1984JCCS315>. Analogous reactions performed in the absence of base gave 91 as a 3-thiol when performed with carbon disulfide, as a 3-hydroxyl with methyl chloroformate, or as a 3-arylamino with arylisothiocyanates in the presence of dicyclohexylcarbodiimide (Scheme 7) <1986JHC1339, 1992IJB467>. 

Carbonyl complexes also react with non-carbon nucleophiles. The resulting carbonic acid derivatives can serve as starting material for the preparation of bis-heteroatom-substituted carbene complexes [93]. Heterocyclic carbene complexes can be obtained from nucleophiles with a leaving group in -position (Table 2.2). 

Alternatively, diazopyrazole (86) reacted with amines to yield triazines which, when treated with activated carbonic acid derivatives, e.g., phosgene, afforded derivatives of 161 (87CB1375). 

Another useful carbonic acid derivative is carbamic acid. Like carbonic acid, carbamic acid is unstable (see Figure 12-42). 

Most important are quantitative solid-state reactions of cyclic carbonic acid derivatives with gaseous or solid amines. These give open-chain amides that can be recyclized in various cases to new products of preparative interest. 

The carbonic acid derivatives involved in method B can also be considered as 0-acylamidoximes but their cydization leads only to 5 -hydroxy-oxadiazoles. 

Ethyl chloroformate reacts with the isonitroso group of amidoximes to give the corresponding carbonic acid derivative which, on heating, splits off ethanol and yields a 3-substituted 5-hydroxyoxadiazole 27, 28, 103, 104). 

Figure 13.7 Examples of carboxylic and carbonic acid derivatives. Ri, R2, R3i R4 denote carbon-centered substituents.

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