Aliphatic esters methyl acetate

Aliphatic Esters Methyl acetate Ethyl acetate... 

The Claisen condensation of an aliphatic ester and a thiazolic ester gives after acidic hydrolysis a thiazolylketone (56). For example, the Claisen condensation of ethyl 4-methyl-5-thiazolecarboxylate with ethyl acetate followed by acid hydrolysis gives methyl 4-methyl-5-thiazolyl ketone in 16% yield. 

Esters of primary aliphatic alcohols show an initial increase in rate with increasing acid concentration, but the curve, illustrated in Fig. 1 for ethyl acetate, passes through a maximum at an intermediate acid concentration (50-60% H2S04), and the rate coefficient subsequently falls almost to zero in the region of 80% acid. Finally, the rate increases slightly between 80% and 100% H2S04. Methyl acetate is rather more reactive than the ethyl ester in above about 50% H2S04, but /i-propyl acetate shows closely similar reactivity, so that the curve for ethyl acetate can be considered to represent the typical behaviour of a primary alkyl ester. 

The final increase in the rate of hydrolysis of the esters of primary aliphatic alcohols, in 85-100% H2SO, is presumably due to acyl-oxygen cleavage, since methyl acetate reacts faster than the ethyl ester, which would not be the case for alkyl-oxygen cleavage. So also may be the rapid hydrolysis of aryl acetates at moderate acidity, since aryl-oxygen cleavage is not expected to be so rapid a reaction. 

A quantitative assessment of the effects of head group bulk on, S k2 and E2 reactions in cationic micelles has been made.148 The kinetics of the acid-catalysed hydrolysis of methyl acetate in the presence of cationic, anionic, and non-ionic surfactants has been reported on.149 The alkaline hydrolysis of -butyl acetate with cetyltrimethylammonium bromide has also been investigated.150 The alkaline hydrolysis of aromatic and aliphatic ethyl esters in anionic and non-ionic surfactants has been studied.151 Specific salting-in effects that lead to striking substrate selectivity were observed for the hydrolysis of /j-nitrophenyl alkanoates (185 n = 2-16) catalysed by the 4-(dialkylamino)pyridine-fimctionalized polymer (186) in aqueous Tris buffer solution at pH 8 and 30 °C. The formation of a reactive catalyst-substrate complex, (185)-(186), seems to be promoted by the presence of tris(hydroxymethyl)methylammonium ion.152... 

Other reductions. Miller et report reduction of benzoic acid and of methyl benzoate to benzyl alcohol and of n-butyl caproate to n-butanol and n-hexanoL Russian investigators" report reduction of aliphatic and aromatic esters to aldehydes, of ortho esters to acetals, of acetals to ethers, and of benzyl ethyl ether to toluene. 

The factor 2.48 puts a on the same scale as Hammett s er, and the k0 values are rate constants for acid and base hydrolysis of acetic acid esters (i.e., R is a methyl group in the reference compound). Usually R is an ethyl or methyl group, but in many cases the rate constants do not depend on the nature of R. Equation 8 is based on the fact that acid hydrolysis rates of substituted benzoic acid esters are only slightly affected by the nature of the substituent, but acid hydrolysis rates of aliphatic esters are strongly affected by substituents. These effects were taken to be caused by steric factors thus log(/c//c0)acid defines s. It is reasonable to assume that steric factors affect base-catalyzed rates in the same way. Substituent effects on base hydrolysis of aliphatic compounds are composed of both polar and steric effects, and subtraction of the latter yields a measure of the former. The parameter a is important because it allows one to evaluate substituent effects on aliphatic reaction rates by a formula analogous to the Hammett equation, or by a bivariate relationship, the Taft-Pavelich equation (Pavelich and Taft, 1957) ... 

Likewise, the substituent constants in the aliphatic series have also been measured from the rates of hydrolysis of a series of aliphatic esters (RCH2CO2CH3), where methyl acetate (CH3CO2CH3) is the parent ester. The effect of the substituent R... 

Contrary to their abundance and essential contribution in fruit flavors, aliphatic and aromatic monofunctional esters are less represented in roasted coffee volatiles. For example methyl formate (F.l) and methyl acetate (F,7) were the only esters identified in a coffee aroma (see Alcohols, Section 5.B) by Merritt et al. (1963), representing 10.3% of the aroma in nearly equal proportions. They do not significantly contribute to the character of the beverage (apart from a few, particularly F.40, F.42 and F.46 which contribute to an off-flavor produced by unhealthy green beans (Bade-Wegner et al., 1998, Full et al., 2000). By way of compensation, when esters are associated, for instance, with heterocyclic rings, thiols or phenols, they can sometimes afford original flavor notes. In this chapter, only relatively simple esters are enumerated and discussed. Some esters with a function either on the acid part or the alcohol part are also mentioned. 

The most suitable solvents are Ce or C7 aliphatic esters or ketones and Cio alkanes. The most common organic solvent in FAAS is 4-methyl-2-pentanone (MIBK = methyl isobutyl ketone). Its nebulization, combustion, and volatilization properties are good for spraying into the flames. Its solubility in water is relatively high (2.15 ml per 100 ml H2O at 30 °C). In addition, its solubility significantly depends on the temperature and the ionic strength of the aqueous phase. The solubility of MIBK in water may be reduced and extraction efficiency increased with addition of amyl acetate (1 10 v/v) or cyclohexane (1 4 v/v). Other solvents commonly used are ethylacetate, butylacetate, and ethylpropionate. 

Christiansen, K Mahadevan, V. Viswanathan C.V. Holman, R.T. (1969). Mass spectrometry of long-chain aliphatic aldehydes, dimethyl acetals and alk-l-enyl ethers. Lipids, Vol.4, No.6, (November 1969), pp. 421-427, ISSN 1558-9307 Christie, W.W. (1988). Equivalent chain-lengths of methyl ester derivatives of fatty acids on gas chromatography A reappraisal. Journal of Chromatography A, Vol.447, pp. 305-314, ISSN 0021-%73... 

Hauser and co-workers have prepared a number of triketones by (1) acylation of benzoylacetone with aliphatic esters employing lithium amide, (2) by twofold aroylation of acetone with methyl esters using sodium hydride, (3) by aroylation and acylation of aliphatic diketones with potassium amide in liquid ammonia and (4) by aroylation of sodioacetoacetaldehyde in the presence of potassium amide. Disodio- and dipotassiobenzoylacetone are not acylated by ethyl acetate or by phenyl propionate. However, dilithiobenzoylacetone and dilithioacetylacetone with an excess of lithium amide are acylated by aliphatic esters. It is usually more convenient to synthesize 4-pyridones directly from these triketones by cyclization with ethanolic ammonia rather than by way of the intermediate Qpyrone. ... 

Aliphatic esters and ketone 50 % by volume ethane acid ethyl ester (ethyl acetate) 50 % by volume 4-methyl-pentanol-(2) (methyl isobutyl ketone)... 

The chemical properties of PVAc are those of an aliphatic ester. Thus, acidic or basic hydrolysis produces poly(vinyl alcohol) and acetic acid or the acetate of the basic cation. Industrially, poly(vinyl alcohol) is produced by a base-catalyzed ester interchange with methanol, where methyl acetate forms in addition to the pol5mieric product. The chemical properties of PVAc can be modified by copolymerization. When a comonomer having a carboxylic acid group or a sulfuric acid group is used, the copolymer becomes soluble in dilute aqueous alkah or... 

It is probable that the molecules of acetone, and also of the lower aliphatic esters, are associated to a slight extent in the liquid state, and, according to Hyland (5), the following pairs of liquids form mixtures of minimum boiling point carbon disulphide and acetone carbon disulphide and methyl acetate carbon disulphide and ethyl acetate ... 

Aliphatic esters in various combinations play a major part in many flavors, particularly fruit flavors 441), Hexyl acetate develops the strongest and most typical odor in Cox s Orange Pippin apples (279). Hexyl 2-methylbutyrate contributes highly to the flavor of Golden Delicious apples (265). Methyl and ethyl esters of ( )-3-hexenoic, (Z)-4-decenoic (32) and )- and (Z)-4-octenoic acids have some importance in the flavor of pineapple 408). Methyl (Z)-4-decenoate (32) and methyl thiohexanoate account for about 56% of the odor provided by the components of the oxygenated fraction of hop oil 202). Ethyl (jE, Z)-2,4-decadienoate (35) is considered as the character impact compound in the aroma of Bartlett pears (227) (Table 2). The application of this pear ester in reconstitution work has been facilitated by the development of highly stereospecific syntheses 405, 407, 457). Isobutyl an-gelate is considered as an essential constituent of Roman camomile oil 85). 

Since the main reaction product is /3-alanine, the propionic acid group evidently migrates more readily than the methyl group. It appears that in aliphatic and alicyclic /3-keto esters the acetic or substituted acetic ester residue migrates in preference to the hydrocarbon residue thus the reaction of substituted acetoacetic esters with hydrazoic acid affords a convenient way to synthesize a-amino acids in excellent yields. ... 

Methyl metacrylates, alcohols, aromatic and aliphatic carbohydrates, acetic ester acids are detected using he vapour-phase method. 

Notable examples of general synthetic procedures in Volume 47 include the synthesis of aromatic aldehydes (from dichloro-methyl methyl ether), aliphatic aldehydes (from alkyl halides and trimethylamine oxide and by oxidation of alcohols using dimethyl sulfoxide, dicyclohexylcarbodiimide, and pyridinum trifluoro-acetate the latter method is particularly useful since the conditions are so mild), carbethoxycycloalkanones (from sodium hydride, diethyl carbonate, and the cycloalkanone), m-dialkylbenzenes (from the />-isomer by isomerization with hydrogen fluoride and boron trifluoride), and the deamination of amines (by conversion to the nitrosoamide and thermolysis to the ester). Other general methods are represented by the synthesis of 1 J-difluoroolefins (from sodium chlorodifluoroacetate, triphenyl phosphine, and an aldehyde or ketone), the nitration of aromatic rings (with ni-tronium tetrafluoroborate), the reductive methylation of aromatic nitro compounds (with formaldehyde and hydrogen), the synthesis of dialkyl ketones (from carboxylic acids and iron powder), and the preparation of 1-substituted cyclopropanols (from the condensation of a 1,3-dichloro-2-propanol derivative and ethyl-... 

Important aroma compounds of black currant berries have been identified mainly by GC-O techniques by Latrasse et al. [119], Mikkelsen and Poll [115] and Varming et al. [7] and those of black currant nectar and juice by Iversen et al. [113]. The most important volatile compounds for black currant berry and juice aroma include esters such as 2-methylbutyl acetate, methyl butanoate, ethyl butanoate and ethyl hexanoate with fruity and sweet notes, nonanal, /I-damascenone and several monoterpenes (a-pinene, 1,8-cineole, linalool, ter-pinen-4-ol and a-terpineol) as well as aliphatic ketones (e.g. l-octen-3-one) and sulfur compounds such as 4-methoxy-2-methyl-butanethiol (Table 7.3, Figs. 7.3, 7.4, 7.6). 4-Methoxy-2-methylbutanethiol has a characteristic catty note and is very important to blackcurrant flavour [119]. 

A number of ketones have been condensed with ethyl cyanoacetate by this procedure. Reactive ketones such as aliphatic methyl ketones and cyclohexanone condense with ethyl cyanoacetate much more rapidly and give better yields of alkyli-dene esters. It is advantageous with such ketones to use a lower ratio of ammonium acetate-acetic acid catalyst.1... 

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