Dimethyl esters of dicarboxylic acids

The conformational characteristics of dimethyl esters of dicarboxylic acids are studies by the NMR and dipole moment method. Conformational energies of the internal CH2-CH2 bonds are determined from the observed 1H-1H vicinal coupling constants. Preferred conformations around the C-C bond are elucidated from the RIS analysis of dipble moments. With the RIS parameters thus established, the orientational correlation between the terminal ester groups is examined. The analysis provides the reason why the odd-even effect in the dipole moment is moderate, and attenuates rapidly with n in the ct.co-diester series. 

The main oxidation products of the methyl esters of aliphatic acids containing n C atoms are methyl esters of dicarboxylic acids C4—C 3, aliphatic acids Ci— Cn-i, and keto- and hydroxy compounds [301—307]. Oxidation of acetates (140—160° C) yield acids, carbon dioxide, hydroxy, and keto compounds (see Table 17). Hydroperoxide is the primary product of oxidation. Oxidation of dimethyl esters of dicarboxylic acids gives monoesters with a lower number of C atoms in the acidic group (see Table 17). Carbon dioxide is formed in parallel with acids and monoesters [308]. All monoesters C 1 Cn 2 etc. are also formed in parallel. This suggests several mechanisms of C—C bond scission in the oxidation, an a-mechanism with only one C—C bond broken to form Cm and C — products, a /3-mechanism with two C—C bonds broken in the /3-position to form Cm, C —m— and C02, etc. The a, /3, and 7-mechanisms of C—C bond scission may be regarded as a result of peroxy radical isomerization to form labile dihydroperoxides, e.g. 

Carbon dioxide formation accompanies the oxidation of esters. In the initiated oxidation of cyclohexanol [319,320] and cumene [320], C02 is formed from dimethyl esters of dicarboxylic acids through an intermediate, probably hydroperoxide, by... 

The direct polyesterification reaction of diacids with glycols is the most important industrial synthetic route to polyester polyols. The second most important synthetic route is the transesterification reaction between dimethyl esters of dicarboxylic or dibasic acids (dimethyl adipate, dimethyl terephthalate, dimethyl carbonate or even polyethylene terephthalate) and glycols (reaction 8.2) [1, 3-8]. 

Early attempts at chain extension took the route of using esters of dicarboxylic acids which had greater reactivity towards the polyester chain ends than simplistic additives such as dimethyl terephthalate [191, 193, 194], but many of the more reactive species gave nonvolatile small-molecule by-products such as phenol, which were difficult to remove. Another early attempt [192] used diisocyanates, but this approach can give imdesirable branching, and the new linkage formed was thermally unstable. Later studies used diisocyanates to chain-extend recycled PET [178]. 

For example, hydrolysis of esters of dicarboxylic acids belongs to such reactions. Thus, dimethyl ester of the oxalic acid is hydrolyzed through two steps... 

The first polyester, developed in the 1940s, involved the polymerization of benzene 1,4-dicarboxylic acid (terephthalic acid) with 1,2-ethanediol (ethylene glycol) to give poly-(ethylene terephthalate), abbreviated PET. Virtually aU PET is now made from the dimethyl ester of terephthahc acid by the following transesterification reaction (Section 14.4C) ... 

Esters of dicarboxylic acids (both methyl and ethyl) usually give very low molecular ions these can be recognized by abundant doublets of (M — OR)" and (M — HOR)" ", and fragments due to subsequent elimination of the other alcohol molecule (M — OR — HOR )". Dimethyl alkanedioates show characteristic fragments (M — CHjCOOCHj)" and COOCH3 the CH2=C(0H)0CH3" ion is abundant, but less prominent than in the spectra of methyl alkanoates. 

Since 3-methylenecyclobutane-l,2-dicarboxylic anhydride is easily converted to 3-methyl-2-cydobutene-l,2-dicarboxylic acid, it is an intermediate to a variety of cyclobutenes. The dimethyl ester of 3-methylenecyclobutane-l,2-dicarboxylic acid is also a versatile compound on pyrolysis it gives the substituted allene, methyl butadienoate, and on treatment with amines it gives a cyclobutene, dimethyl 3-methyl-2-cyclobutene-l,2-di-carboxylate. ... 

The ultraviolet absorption spectra of compounds II from D-glucose and XI from D-fructose show an absorption band at 250 m/j, in accordance with their furan character.9 The product of periodate oxidation (V) and the dimethyl ester of the derived dicarboxylic acid (III) absorb at 285 and 262 m/i, respectively. The anhydrides of the condensates, XXXIV, do not exhibit selective absorption in the ultraviolet region, but the product of their oxidation (XXXVI) with periodic acid shows8 a band at about 270 m/i. 

To a mixture of 360 g 50% KOH and 138 ml methanol, add with stirring at -5° 70.5 g dimethyl ester of acetone dicarboxylic acid (dimethyl-beta-ketoglutarate — see method 3 for preparation) and let temperature rise to about 25° over V2 hour. Let stand ten minutes, cool to 0° and add 65 ml ether. Filter, wash precipitate with 65 ml ethanol and 150 ml ether at 0C to get 75 g (III). To 322 ml 1N HCI at 80c, add 41.1 g (I I) and stir twenty minutes cool to 10°, add 211 ml IN HCI, 98.2 g (Ml). 26.4 g Na acetate and 28.2 g methylamine HCI. Stir four hours at room temperature, cool to 10°, and saturate with 410 g KOH. Extract four times with methyl-Cl or benzene (75 ml each, fifteen minutes stirring) and evaporate in vacuum to get the methyl ester of tropan-3-one-2-COOH (IV), which precipitates from the oil (can distill 85/0,2). Test for activity. Dissolve 28.3 g (IV) in 170 ml 10% sulfuric acid cool to -5° and treat with 3.63 kg 1.5% Na-Hg amalgam with vigorous stirring at 0°. See below for easier methods of reducing (IV),... 

Svendsen, J.S. Sydnes, L.K. Whist, J.E. Mass Spectrometric Study of Dimethyl Esters of Trimethylsilyl Ether Derivatives of Some 3-Hydroxy Dicarboxylic Acids. Org. Mass Spectrom. 1987,22,421-429. 

The methyl esters of dicarboxylic acids88 give no dicarboxylic products only mono-carboxylic acid derivatives are formed. Dimethyl succinate, dimethyl maleate and dimethyl acetylenedicarboxylate over potassium tetrafluorocobaltate(III) at 270-350"C all give mixtures of (crude products are converted into ethyl esters) ethyl pentafluoropropanoate and ethyl... 

Many substances can serve as the stationary phase for gas chromatographic separations of methyl esters in most cases polyester, polyether, or silicone greases are used. Percival (18) has investigated the composition of polyesters by methanolysis with sodium methyl oxide. The dimethyl esters of the dicarboxylic acids present in the composition and free glycols are formed and subsequently are separated at temperatures between 110° and 180° C. on a column of GE silicone SF-96 and Fluoropak 80. It should be possible to adapt this method to the analysis of polyesters used as plasticizers. 

A laboratory preparation of the simplest of these catenation compounds. two interlocking rings, has been carried out at AT T Bell Laboratories. They started wilh the dimethyl ester of a 34-carbon paraffinic dicarboxylic acid, CH ,OOC-(CH )j2-COOCHi, which was reacted in a suspension of metallic sodium in xylene with acelic acid to condense the terminal ester groups to form an aceloin ring compound. 

Figure 6.- Total Ion Chromatogram of the thermal degradative products obtained after pyrolysis of the HA isolated from the Konin (Poland) brown coal in the presence ot TMAH. Key labels for aromatic compunds are (9) 4-memoxybenzenecarboxylic acid methyl ester, (14) benzenedicarboxylic acid dimethyl ester, (16) 3,4-dimelhoxybenzenecarboxylic acid methyl ester, (17) 3,4-dimethoxybenzeneacetic acid methyl ester, (18) 4-medioxycinnamic acid methyl ester, (19) 3,4,5-trimethoxy-l-ethylbenzene. Key labels for aliphatic compounds are (Cn) monocarboxylic acid methyl esters, (Cn l) unsaturated monocarboxylic acid methyl esters, (Cn) dicarboxylic acid dimethyl esters.

The first example of such a methylenecyclopropane rearrangement was the isomerization of dimethyl rraM -3-methylenecyclopropane-l,2-dicarboxylate (the dimethyl ester of Feist s acid, 1) which occurred upon heating to about 200°C. It was not until 1952 that this reaction was formulated in proper structural terms. Thus, 1 rearranged to a 1 1 mixture of methyl (Z)- and ( )-2-(methoxycarbonylmethylene)cyclopropanecarboxylate (2). ... 

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