Esters of Dibasic Acids

More interesting derivatives are the mixed esters in which the free hydroxyl groups of cellulose acetate are esterified with the dibasic acid 

Partial esterification of cellulose with p-toluenesulfonyl chloride may be accomplished in the presence of pyridine, or by reaction with alkali cellulose. The tosyl (p-toluenesulfonyl) group has been shown to react quite readily with the primary hydroxyl group of cellulose but much more slowly with the secondary groups. The reaction in the presence of pyridine must be carried out at low temperatures to prevent the introduction of nitrogen and halogen from side reactions.  

Use of the tosyl derivative of cellulose for theoretical study is important. Cramer and Purves have prepared tosyl derivatives of acetone-soluble cellulose acetate. By treatment with sodium iodide, which replaces tosyl groups in the primary position by iodine, they have been able to measure the proportions of primary and secondary hydroxyl groups present in the original product. 

By treatment with aliphatic primary or secondary amines, tosyl groups on cellulose (a low-substituted cellulose, such as methylcellulose, was employed) may be replaced by substituted amino groups. The products obtained are insoluble in water but dissolve readily in dilute acid. 

Organic isocyanates react with cellulose in the presence of dry pyridine to produce the corresponding N-substituted carbamates. Aliphatic isocyanates bring about only partial esterification, while aromatic reagents under proper conditions react readily and completely. Cellulose N-phenylcarbamate is soluble in several organic solvents and is extremely stable toward either acid or alkaline decomposition. Incomplete esteri- 

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Sometimes a large proportion of sulphuric acid is employed (see below under esters of dibasic acids). The good yields thus obtained are partially due to the removal of water by the acid as well as to the catalytic effect. 

This procedure is speedy, economical, and employs materials which are readily available. It is not satisfactory for esters of dibasic acids. 

This preparation illustrates the use of the copper-chromium oxide catalyst in the r uotion of esters of dibasic acids to glycols ... 

Other constituents may be added to assist in the formation of uniform beads or to influence the use properties of the polymers through plasticization or cross-linking. These include lubricants, such as lauryl or cetyl alcohol and stearic acid, and cross-linking monomers such as di- or trivinylbenzene, diaHyl esters of dibasic acids, and glycol dimethacrylates. 

Molecular ions are not always observed for methyl esters of dibasic acids however, methyl esters of all dibasic acids lose 31 and 73 Daltons from their molecular ions. By adding 31 or 73 to the appropriate ions, the molecular weight can be deduced. 

Table VII.—Comparative Saponification Rates at 25°C of Carboethoxy Groups in Di- and Monoethyl Esters of Dibasic Acids ...

Synthetic esters, (a) primarily esters of dibasic acids such as adipic and sebacic, though in Europe some monobasic acid esters have been prepared and used (h) organic esiers of phosphoric and silicic acid, which have some advantage of being more lire-resislant than Ihe other organic compounds bm which are subject to hydrolysis on exposure to water,... 

Many years ago, Brown and Walker3 found that by electrolysis of mono-esters of dibasic acids, carbon dioxide was removed, and the residues condensed to form a dibasic ester of higher molecular weight. 

Esters of dibasic acids ROOC(CH2) COOR, in general, give recognizable molecular ion peaks. Intense peaks are found at [R00C(CH2) C=0]+ and at [ROOC(CH2) ]+. 

Ketones, condensation—Continued with esters of dibasic acids, 54 with a-halo esters, 34, 177, 254, 255, 351... 

Both the Bouveault-Blanc and catalytic hydrogenation proceduresare popular methods for the preparation d dials from esters of dibasic acids. The reduction of malonic esters, /3-keto esters, and /3-hydroxy esters by the usual catalytic hydrogenation procedure results in extensive bydrogenolysis of the carbon chain to give lower-molecular-weight alcohols. However, with relatively large amounts of catalyst... 

Partial saponification of malonic ester occurs with cold alcoholic potassium hydroxide to give potassium ethyl malonate in 82% yield. Esters of dibasic acids having the carboxyl groups farther apart are cleaved in a similar manner under these conditions, e.g., the preparation of the halfester of a-methylpimelic acid (59%)- ... 

Carboalkoxy acyl halides are made from mono esters of dibasic acids and thionyl chloride or phosphorus pentachloride. Examples are numerous. Halides with the ester group in the beta position are unstable to prolonged heating. Alkyl halide is eliminated with the formation of an anhydride. Under certain conditions a rearrangement occurs in the preparation of ester acid chlorides. The product obtained is a mixture of the expected compound and its isomer in which the ester and acid chloride groups are interchanged, viz., ROjCCHR (CI ) CO,H — RO,C(CH,) CHR COQ. The cyclic anhydride is a likely intermediate. ... 

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