Ester crystallinity

Oxahc acid reacts with various metals to form metal salts, which are quite important as the derivatives of oxahc acid. It also reacts easily with alcohols to give esters. Crystalline dimethyl oxalate is, for example, produced by the reaction of oxahc acid dihydrate and methanol under reflux for a few hours. When oxahc acid is treated with phosphoms pentachloride, oxalyl chloride, ClCOCOCl, is formed (6). 

C2H4N2O3, NH2CONHCOOH. Unknown in the free state as it breaks down immediately to urea and COi- The NH4, Ba, Ca, K and Na salts are known and are prepared by treating ethyl allophanate with the appropriate hydroxide. The esters with alcohols and phenols are crystalline solids, sparingly soluble in water and alcohol. They are formed by passing cyanic acid into alcohols or a solution of an alcohol or phenol in benzene. The amide of allophanic acid is biuret. Alcohols are sometimes isolated and identified by means of their allophanates. 

CH OfiSj, H2C(S03H)2- a colourless, crystalline solid which readily absorbs water vapour decomposes on distillation. The potassium salt is prepared by heating methylene chloride with an aqueous solution of potassium sulphite under pressure at 150-I60" C. The free acid is obtained by decomposing the sparingly soluble barium salt with sulphuric acid. The aryl esters are very stable, but the alkyl esters decompose on heating to give ethers. Resembles malonic acid in some of its reactions. 

C7H7CIO1S, p-CHjCjsH SOjCI. Colourless crystals, m.p. 7l°C, formed by the action of chlorosulphonic acid on toluene. Esters of toluenesulphonic acid are frequently called tosylatesand their formation tosylation. Many tosylates are easily obtained crystalline, and the reaction is thus of considerable importance. 

Give crystalline esters with 3,5 dinitrobenzoyl chloride. 

Ethyl oxalate is the only liquid ester which gives this rapid separation of the amide, which is therefore characteristic. Methyl and ethyl formate react rapidly with ammonia, but the soluble formamide does not separate methyl succinate gives crystalline succinamide after about I hour s standing, other esters only after a much longer time. The solid esters, other than methyl oxalate, are either soluble in water and remain so when treated with ammonia, or alternatively are insoluble in water and hence clearly not methyl oxalate. 

Add 0-5-1 ml. of the alcohol, cork the flask loosely, and heat on a water bath for 10 minutes secondary and tertiary alcohols require longer heating (up to 30 minutes). Cool the mixture, add 10 ml. of 5 per cent, (or saturated) sodium bicarbonate solution, break up the resulting solid ester with a stirring rod (alternatively, stir until crystalline), and filter at the pump wash with a little sodium bicarbonate solution, followed by water, and then suck as dry as possible. Dissolve the crude... 

Drop 1 g. of sodium into 10 ml. of ethyl alcohol in a small flask provided with a small water condenser heat the mixture until all the sodium has dissolved. Cool, and add 1 g. of the ester and 0-5 ml. of water. Frequently the sodium salt of the acid will be deposited either at once or after boiling for a few minutes. If this occurs, filter oflF the solid at once, wash it with a little absolute ethyl alcohol (or absolute methylated spirit), and convert it into the p-bromophenacyl ester, p-nitro-benzyl ester or S-benzyl-tso-thiuronium salt (for experimental details, see Section 111,85). If no solid separates, continue the boiling for 30-60 minutes, boil oflF the alcohol, allow to cool, render the product just neutral to phenolphthalein with dilute sulphuric or hydrochloric acid, convert the sodium salt present in solution into a crystalline derivative (Section 111,85), and determine its melting point. 

The hydrazides are often crystalline and then serve as useful derivatives. Esters of higher alcohols should be converted first to the methyl esters by boiling with sodium methoxide in methanol (see under AT-benzylamides). 

To prepare the solid phenyldlazonlum chloride or sulphate, the reaction is conducted in the absence of water as far as possible. Thus the source of nitrous acid is one of its organic esters (e.g., amyl nitrite) and a solution of hydrogen chloride gas in absolute alcohol upon the addition of ether only the diazonium salt is precipitated as a crystalline solid, for example ... 

Aromatic esters usually burn with a smoky flame, possess reasonably high boiling points, and are (particularly esters of phenols) sometimes crystalline solids. Phenyl esters usually give phenol upon distillation with soda hme (see Section IV,175 for general details). 

Saponification of esters. Aqueous sodium hydroxide method. To hydrolyse an ester of an alcohol, reflux 5-6 g. with 50 ml. of 20 per cent, sodium hydroxide solution for 1-2 hours or until the ester layer disappears. Distil the alkahne mixture and collect about 6 ml. of distillate. This will contain any volatile alcohol formed in the saponification. If the alcohol does not separate, i.e., is water-soluble, saturate the distillate with sohd potassium carbonate an upper layer of alcohol is then usually formed. (The alcohol may be subsequently identified as the 3 5-dinitrobenzoate see Section 111,27,2.) Cool the residual alkahne mixture, and acidify it with dilute sulphuric acid. If no crystalline acid is precipitated, the acid may frequently be isolated by ether extraction, or it may be distilled from the acidified solution and isolated from (or investigated in) the distfllate. (The acid may be subsequently identified, e.g., as the S benzyl wo-thiuronium salt see Section 111,85,2.)... 

Unlike most crystalline polymers, PVDF exhibits thermodynamic compatibiUty with other polymers (133). Blends of PVDF and poly(methyl methacrylate) (PMMA) are compatible over a wide range of blend composition (134,135). SoHd-state nmr studies showed that isotactic PMMA is more miscible with PVDF than atactic and syndiotactic PMMA (136). MiscibiUty of PVDF and poly(alkyl acrylates) depends on a specific interaction between PVDF and oxygen within the acrylate and the effect of this interaction is diminished as the hydrocarbon content of the ester is increased (137). Strong dipolar interactions are important to achieve miscibility with poly(vinyhdene fluoride) (138). PVDF blends are the object of many papers and patents specific blends of PVDF and acryflc copolymers have seen large commercial use. 

Dimenhydrinate. Dimenhydrinate [523-87-5] (Dramamine) (18) is a white crystalline, odorless powder that melts between 102 and 107°C. It is sparingly soluble in water, freely soluble in ethanol and chloroform, and sparingly soluble in diethyl ether. Dimenhydrinate is prepared by combining dimethylaminoethyl ben2hydryl ester with 8-ch1orotheophy11ine and refluxing in an isopropyl alcohol solution. The crystalline precipitate of dimenhydrinate that forms on cooling is collected by filtration, washed with cold ethyl acetate, and dried. 

A cross-linked and crystalline copoly(ester—imide) containing an alkene function was made by reaction of an unsaturated diacid chloride containing a cychc imido group with ethylene glycol at low temperature (27). 

A left-handed double-heUcal stmcture has been proposed for geUan in the crystalline state, based on x-ray diffraction studies (227). The presence of acetyl groups presumably dismpts interchain aggregation, since these groups are postulated to be on the outside of the heUces. The role played by acetyl and glyceryl ester groups and their influence on the double-heUcal stmcture has been studied using computet models (232). 

Poly(ethylene terephthalate). PET is a crystalline material and hence difficult to plasticize. Additionally, since PET is used as a high strength film and textile fiber, plasticization is not usually required although esters showing plasticizing properties with PVC may be used in small amounts as processing aids and external lubricants. Plasticizers have also been used to aid the injection mol ding of PET, but only at low concentrations. 

Carbon Cha.in Backbone Polymers. These polymers may be represented by (4) and considered derivatives of polyethylene, where n is the degree of polymeriza tion and R is (an alkyl group or) a functional group hydrogen (polyethylene), methyl (polypropylene), carboxyl (poly(acryhc acid)), chlorine (poly(vinyl chloride)), phenyl (polystyrene) hydroxyl (poly(vinyl alcohol)), ester (poly(vinyl acetate)), nitrile (polyacrylonitrile), vinyl (polybutadiene), etc. The functional groups and the molecular weight of the polymers, control thek properties which vary in hydrophobicity, solubiUty characteristics, glass-transition temperature, and crystallinity. 

Licjuid Crystals. Ferroelectric Hquid crystals have been appHed to LCD (Uquid crystal display) because of their quick response (239). Ferroelectric Hquid crystals have chiral components in their molecules, some of which are derived from amino acids (240). Concentrated solutions (10—30%) of a-helix poly(amino acid)s show a lyotropic cholesteric Hquid crystalline phase, and poly(glutamic acid ester) films display a thermotropic phase (241). Their practical appHcations have not been deterrnined. 

Subsequent dehydrohalogenation afforded exclusively the desired (Z)-olefin of the PGI2 methyl ester. Conversion to the sodium salt was achieved by treatment with sodium hydroxide. The sodium salt is crystalline and, when protected from atmospheric moisture and carbon dioxide, is indefinitely stable. A variation of this synthesis started with a C-5 acetylenic PGF derivative and used a mercury salt cataly2ed cyclization reaction (219). Although natural PGI has not been identified, the syntheses of both (6R)- and (65)-PGl2, [62777-90-6] and [62770-60-7], respectively, have been described, as has that of PGI3 (104,216). 

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