Butyrate effect

One of the most sensitive tests of the dependence of chemical reactivity on the size of the reacting molecules is the comparison of the rates of reaction for compounds which are members of a homologous series with different chain lengths. Studies by Flory and others on the rates of esterification and saponification of esters were the first investigations conducted to clarify the dependence of reactivity on molecular size. The rate constants for these reactions are observed to converge quite rapidly to a constant value which is independent of molecular size, after an initial dependence on molecular size for small molecules. The effect is reminiscent of the discussion on the uniqueness of end groups in connection with Example 1.1. In the esterification of carboxylic acids, for example, the rate constants are different for acetic, propionic, and butyric acids, but constant for carboxyUc acids with 4-18 carbon atoms. This observation on nonpolymeric compounds has been generalized to apply to polymerization reactions as well. The latter are subject to several complications which are not involved in the study of simple model compounds, but when these complications are properly considered, the independence of reactivity on molecular size has been repeatedly verified. 

Other. 2-Nitro-1-butanol is an excellent solvent for many polyamide resins, cellulose acetate butyrate, and ethylceUulose. It can be utilized in paint removers for epoxy-based coatings. 2-Hydroxymethyl-2-nitro-l,3-propanediol is usebil for control of odors in chemical toilets. Its slow release of formaldehyde ensures prolonged action to control odor, and there is no reodorant problem which sometimes is associated with the use of free formaldehyde. 2-Hydroxymethyl-2-nitro-l,3-propanediol solutions are effective preservative and embalming fluids. The slow Uberation of formaldehyde permits thorough penetration of the tissues before hardening. 

Oxidation of butyraldehyde to butyric acid [107-92-6]is most commonly carried out employing air or oxygen as the oxidant. Alternatively, organic oxidants, eg, cumene hydroperoxide, can also be employed effectively to give high yields of butyric acid, (4). 

Other mixed esters, eg, cellulose acetate valerate [55962-79-3] cellulose propionate valerate [67351-41-17, and cellulose butyrate valerate [53568-56-2] have been prepared by the conventional anhydride sulfuric acid methods (25). Cellulose acetate isobutyrate [67351-38-6] (44) and cellulose propionate isobutyrate [67351-40-0] (45) have been prepared with a 2inc chloride catalyst. Large amounts of catalyst and anhydride are required to provide a soluble product, and special methods of delayed anhydride addition are necessary to produce mixed esters containing the acetate moiety. Mixtures of sulfuric acid and perchloric acid are claimed to be effective catalysts for the preparation of cellulose acetate propionate in dichi oromethane solution at relatively low temperatures (46) however, such acid mixtures are considered too corrosive for large-scale productions. 

These compounds yield, on hydrolysis, the free acids, which, like all acids containing two carbo.xyl groups attached to the same carbon atom, lose COj on heating. Thus, ethyl malonic acid yields butyric acid. In this way the synthesis of monobasic acids may be readily effected. Malonic ester, moreover, may be used in the preparation of cyclic compounds as well as of tetrabasic and also dibasic acids of the malonic acid series ( Perkin). To give one illustration malonic ester, and ethylene bromide in presence of sodium alcoholate, yield triniethyleiic dicarbo.xylic ester and tetramethylene tetracarbo.xylic ester. The first reaction takes place in two steps,... 

A very interesting steric effect is shown by the data in Table 7-12 on the rate of acid-catalyzed esterification of aliphatic carboxylic acids. The dissociation constants of these acids are all of the order 1(T, the small variations presumably being caused by minor differences in polar effects. The variations in esterification rates for these acids are quite large, however, so that polar effects are not responsible. Steric effects are, therefore, implicated indeed, this argument and these data were used to obtain the Es steric constants. Newman has drawn attention to the conformational role of the acyl group in limiting access to the carboxyl carbon. He represents maximum steric hindrance to attack as arising from a coiled conformation, shown for M-butyric acid in 5. 

A low acid polyvinyl butyral-based pretreatment primer ( etch or wash primer are alternative names) is usually advantageous as the first treatment of a metal-sprayed surface before painting. Up to an equal volume of spirit soluble phenolic resin is used as a diluent to the polyvinyl butyral of conventional pretreatment primers. This has an incidental, but particularly valuable effect, in reducing the free acid available to penetrate into the pores of the coating. The modified pretreatment primer is highly water resistant and this helps to avoid damage due to condensation. 

The standard etch primer (WP-1, DEF-1408) consists of two solutions, one containing polyvinyl butyral resin and zinc tetroxychromate in ethyl alcohol with n-butanol, and the second containing phosphoric acid and ethyl alcohol. It is essential that a small critical amount of water be present in the latter. The two solutions are mixed in appropriate ratio for use the mixture deteriorates and should be discarded when more than 8 h old. Single-pack etch primers of reasonable shelf life are available but contain less phosphoric acid than the above and are not considered to be so effective. 

Acetylated polysaccharides form part of the structure of wood, the acetyl radical constituting some 2-5Vo by weight of the dry wood. Hydrolysis to free acetic acid occurs in the presence of moisture at a rate varying from one species to another a wood of lower acetyl content can liberate acetic acid much faster under given conditions than another wood of higher content Small quantities of formic, propionic and butyric acids are also formed but their effects can be neglected in comparison with those of acetic acid. There is a broad, but only a broad, correlation between the corrosivity of a wood and its acidity. The chemistry of acetyl linkage in wood and of its hydrolysis has been examined in some detail. ... 

Moisture Deteriorating effects of moisture are well known as reviewed early in this chapter (OTHER BEHAVIOR, Drying Plastic). Examples for high moisture applications include polyphenylene oxide, polysulfone, acrylic, butyrate, diallyl phthalate, glass-bonded mica, mineral-filled phenolic, chlorotrifluoroethylene, vinylidene, chlorinated polyether chloride, vinylidene fluoride, and fluorocarbon. Diallyl phthalate, polysulfone, and polyphenylene oxide have performed well with moisture/steam on one side and air on the other (a troublesome... 

The ability to disperse the calcium soap formed from a given amount of sodium oleate has been studied for a number of a-sulfo fatty acid esters with 14-22 carbon atoms [28,30]. In principle, the lime soap dispersion property increases with the number of C atoms and the dissymmetry of the molecule. Esters with 14 C atoms have no dispersion power and in the case of esters with 15-17 carbon atoms the least symmetrical are the better lime soap-dispersing agents. However this property does not only depend on the symmetry but on the chain length of the fatty acid group. For example, methyl and ethyl a-sulfomyristate have better dispersing power than dodecyl propionate and butyrate. The esters with 18 and more carbon atoms are about equal in lime soap dispersion power. Isobutyl a-sulfopalmitate is the most effective agent under the test conditions. 

The following conclusions emerge. The rate constant of the monomer addition to oc-lithio-iso-butyrate (the monomeric living polymethyl methacrylate ) is much greater than any other, the ratio kt / k2 20 reflecting the ion stabilizing effect of the... 

The current-potential relationship indicates that the rate determining step for the Kolbe reaction in aqueous solution is most probably an irreversible 1 e-transfer to the carboxylate with simultaneous bond breaking leading to the alkyl radical and carbon dioxide [8]. However, also other rate determining steps have been proposed [10]. When the acyloxy radical is assumed as intermediate it would be very shortlived and decompose with a half life of t 10" to carbon dioxide and an alkyl radical [89]. From the thermochemical data it has been concluded that the rate of carbon dioxide elimination effects the product distribution. Olefin formation is assumed to be due to reaction of the carboxylate radical with the alkyl radical and the higher olefin ratio for propionate and butyrate is argued to be the result of the slower decarboxylation of these carboxylates [90]. 

Later on the crucial role played by the solvent was enlightened in the protease-catalyzed resolution of racemic amines [26]. As shown in Table 1.3, the ratio of the initial rates of acylation of the (S)- and the (Ji)-enantiomers or racemic a-methyl-benzylamine (9) varied from nearly 1 in toluene to 7.7 in 3-methyl-3-pentanol. Similarly, the same authors found a significant solvent effect for the subtilisin-catalyzed transesterification of racemic 1-phenylethanol (10) using vinyl butyrate as acyl donor (Table 1.4 [27]). 

Winters WD, Kott KS Continuum of sedation, activation and hypnosis or hallucinosis a comparison of low dose effects of pentobarbital, diazepam or gamma-hydroxy-butyrate in the cat. Neuropharmacology 18 877—884, 1979... 

HBD is a biochemical rather than electrophoretic assessment of the LD isoenzyme which is associated with heart. All five isoenzymes of LD exhibit some activity toward cx-hydroxy-butyrate as substrate, but heart LD shows the greatest activity. Serum HBD measurement is not as valuable as the electrophoretic determination of heart LD isoenzyme. High HBD activity has also been found in diseases of the liver. Rises associated with the hepatic effects of congestive heart failure can be disconcerting in the differential diagnosis of myocardial infarction. Wilkinson has used the serum HBD/LD ratio for the differentiation of myocardial disease from other disorders in which HBD activity is elevated, whereas Rosalki has not found the ratio to be helpful (39). 

MENZEL T, SCHAUBER J, KRETH F, KUDLICH T, MELCHER R, GOSTNER A, SCHEPPACH W, LUHRS H (2002) Butyrate and aspirin in combination have an enhanced effect on apoptosis in human colorectal cancer cells. Eur J Cancer Prev. 11 271-81. 

In the reaction, it was essential to use an IL as a co-solvent. Lozano, Iborra and co-workers recently reported an interesting stabilizing effect of two types of water-immiscible ILs ([emim][TFSI] and [BuMe3N][TFSI]) for CAL-B-catalyzed transesterification of vinyl butyrate. The synthetic activity and the stability of the enzyme in these IL solvent systems were markedly enhanced as compared to those in hexane. CAL-B maintained its activity higher than 75% after 4 days of incubation in [emim][TFSI] solvent, while it showed an activity of only 25% when incubated in both water and hexane media at 50°C. Comparison of the ratio of a-helix and (3-sheet by CD spectra showed the activity was closely related with a-helix content which reduced to 31% immediately after lipase was added to hexane and had reached only 2% after 4 days in hexane. On the contrary, no significant reduction of a-helix content was... 

Figure 13 Temperature effect in lipase PS-C Il-catalyzed resolution of ( )-13 with vinyl acetate ( ), vinyl butyrate ( ), and vinyl 3-phenylpropanoate (A) in...

More recently chitosan polymers which are derivatives of chitin materials have evoked interest due to their bioactivity and biodegradability. For example, N-carboxybutyl chitosan has been show to effectively promote wound healing (9). Acetate, and butyrate derivatives of chitosan have decreased blood clotting time significantly (10). 

Christl SU, Eisner HD, Dusel G, et al. 1996. Antagonistic effects of sulfide and butyrate on proliferation of colonic mucosa—A potential role for these agents in the pathogenesis of ulcerative colitis. Dig Dis Sci 41 2477-2481. 

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