Phthalic esters

Aminothiophenes and 3-aminobenzo[Z)]thiophene undergo thermal [2 + 2] cycloaddi-tion reactions with activated alkynes. The reactions are solvent dependent thus in non-polar solvents at -30 °C, 3-pyrrolidinothiophene adds to DMAD to give a [2 + 2] cycloadduct which is ultimately converted into a phthalic ester. In methanol, however, a tricyclic product is formed (Scheme 54) (81JOC424. ... 

Dicarbomethoxyacetylene has also been added to the pyrrolidine enamine derivative of acetylacetone, demonstrating a new synthesis of phthalic esters (345). A 3-acylpyridine synthesis was achieved by the addition of an acetylenic aldehyde to the vinylogous amide derived from ammonia and dihydroresorcinol (346). 

Two distinct bodies were thus obtained, which, on hydrolysis yielded the corresponding menthols, of which one is inactive menthol (melting-point 34° C. boiling-point, 16 mm., 103° to 105° C. acid phthalic ester, melting-point 129° to 131° C.), the other, neomenthol crystallising from petroleum spirit in prismatic tables melting at 51° C. boiling-point,... 

Takahashi T. 1977. Biochemical studies on phthalic esters II. Effects of phthalic esters on mitochondrial respiration of rat liver. Biochem Pharmacol 26 19-24. 

Actually, this is not that difficult to understand. We all know that the more stable form of diesters between fumarate and maleate is the fumarate due to the trans configuration, which minimizes the crowdedness of the esters. In the case of phthalic esters, the aromatic esters cannot possibly rotate to any trans forms and are therefore in a state with a high strain energy. In order to release this energy, these esters would rather prefer to kick-off the esters. This is why they are so prone to attack by hydrolysis, and is why GP resins will fail in any water-immersion type of test, especially under elevated temperature. 

The elution order of phthalic esters is related to the carbon chain length. The longer the chain length, the shorter the retention time in normal-phase liquid chromatography, and the elution order is reversed in reversed-phase liquid... 

T. Takahashi, A. Tanaka, Biochemical Studies on Phthalic Esters. V. Comparative Studies on in vitro Hydrolysis of Di-V-butyl Phthalate Isomers in Rats Arch. Toxicol. 1989, 63, 72-74. 

Jonsson, S. and Baun, A. Toxicity of mono- and diesters of o-phthalic esters to a crustacean, a green alga, and a bacterium. Environ. Toxicol Chem., 22(12) 3037-3043, 2003. 

Uhde E, Bednarek M, Fuhrmaim F, Salthammer T (2001) Phthalic esters in the indoor environment-test chamber studies on PVC-coated wallcoverings. Indoor Air 11 150-155... 

Wang P, Wang SL, Fan CQ (2008) Atmospheric distribution of particulate and gas phase phthalic esters (PAEs) in a Metropolitan City, Nanjing, East China. Chemosphere 72 1567-1572... 

During all of these isolation procedures, special care should be taken to avoid contamination of the samples by plasticizing agents (for example, phthalic esters) which may be derived from the ion-exchange resins or plastic vessels, and which may disturb the following analytical procedures. Thus, use of plastic materials should be largely avoided, and the sialic acids should be processed and stored in glass vessels. 

Non-volatile phthalic esters, (e.g. butyl phthalate) are also used for the manufacture of some nitrocellulose and nitroglycerine powders. 

CA 50, 2173(1956)(Detection, distinction detn of phthalic esters in propints)... 

Analysis of phthalic esters in propints) 15) L. Marvillet, MP 42, 247-60 (I960) CA 55, 14917 (1961) (Analysis of phthalic esters in propints) 16) CondChem-Dict(l961), 360 16a) MIL-STD-286A(Aug... 

CA 55, 14917(1961) (Quantitative analysis by chromatographic methods of phthalic esters in proplnts) 10) ProplntManual SP1A/M2(1962) (Unit Nos 4 6, 260, 385 ... 

Sensitized photocycloaddition of thiophene and 2,5-dimethylthiophene to acetylenedicar-boxylic ester leads to the phthalic esters (303) (73CB674). In the mechanism suggested, the triplet state of the thiophene adds to the alkyne to form a biradical, which cyclizes to the... 

Recently, it has been shown that 2-pyridones with the nitrogen atom substituted by alkyl,262 aryl, or methoxyl265 do undergo Diels-Alder reactions. Heating l-methyl-2-pyridone with DMAD to 195°, the first successful example studied,262 gave 51, which was thought to be formed via 49 as shown. Under milder conditions,265 Diels-Alder adducts (cf. 49) can be isolated and, on further heating, yield phthalic esters and isocyanates. 

After removal of barium sulfate and fractionation of the alkaloid salts, the glycol sulfate ester is recovered as alkali salt and saponified -with alkali.48, 48 The method is tedious and not yet well developed, but it may be noted that the glycols cannot be resolved by the phthalic ester procedure described below because they tend to form polymeric esters instead of simple hydrogen phthalates when treated with phthalic anhydride. 

Emission ofDEHP from PVC wall coverings (containing 30%phthalic esters) was measured in a test chamber at room temperature, maximum concentration of 0.94 g/m3 for DEHP in air over 14-day test period (Udhe et al. 2001). Other citations within this reference noted that DEHP in test chambers was not detectable at room temperature, but maximum concentrations of 5.2 and 2 g/m3 were measured at 60 and 40 °C, respectively. Increases in DEHP emissions with increasing ambient temperature are especially... 

Oishi S, Hiraga K. 1980b. Effect of phthalic esters on mouse testes. Toxicol Lett 5 413-416. 

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