Long chain alkyl bromides

Tab. 5.9 Alkylation of 3,4-dihydroxybenzaldehyde with long chain alkyl bromides under the action of MW + PTC conditions.

Polyetherpolyamine Span sorbitan surfactant Quatemized polyetherpolyamines reacted with a long-chain alkyl bromide BJ Unichem (Pakulski, 2001) CSM (Huo et al, 2001)... 

Therefore, the nucleophilic fluorination (Finkelstein reaction) with naked fluoride generated from metal fluoride by the aid of crown ether reported by Liotta is highly advisable. KF/18-crown-6/acetonitrile system was successfully used in the conversion of short chain alkyl bromides to the corresponding fluorides. However, in cases of long chain alkyl bromides, only unsatisfactory results were obtained. Thus, modification of the reaction conditions were undertaken. 

All the common reagents for the etherification reaction of cellulose are either epoxides or halides. Ethylene oxide (EO), propylene oxide (PO) and alkyl glycidyl ethers are examples of epoxides and monochloroacetic acid (MCA), methyl chloride (MC), ethyl chloride (EC) and long-chain alkyl bromides are examples of halides that are commonly used. The reactions are performed at elevated temperature. Reactions of volatile compounds such as EO, PO, MC and EC require a pressurized reaction vessel. 

Hexadecyltrimethylammonium bromide (HTMAB) was included in the investigation because it had been employed previously. The past success of HTMAB was attributed to its long-chain alkyl group. Mimicking a long polymer chain, the hexadecyl group probably aided in the solvation of PET. 

The cobalt-catalysed reaction between aryl bromides and Grignard reagents assisted by IMes HCl is also known, however the substrate scope is quit narrow and good yields are only obtained when non-branched long chain alkyl magnesium chlorides are used as coupling reagents [80] (Scheme 6 19)... 

Ammonium salts with two different alkyl chains were prepared directly via subsequent alkylations of dimethylamine with primary bromides and crystallization. Commercial hexadecyl-methylamine can be conveniently applied in the same way in order to convey functionality to cationic synkinons. A recent example describes subsequent alkylations with a small functional and a long-chain primary bromide (Scheme 2.4). A-acylated / -phenylenediamine was also alkylated at the second nitrogen atom which had two different alkyl chains, with or without extra functionality . After deacylation, this head group can be diazotized or coupled oxidatively with various heterocycles in water (Scheme 2.4). Photoactive and coloured membrane surfaces are thus obtained. Phenylene-diamine, pyridine and in particular A-methyl-4,4-bipyridinium chloride are relatively weak nucleophiles. Substitution of bromides is slow and the more reactive iodides can rarely be obtained commercially, but the selection of nitromethanes as solvent for bromide substitution is of great help as well as the addition of sodium iodide to enforce a Finkelstein reaction or a combination of both. 

J. N. Gregory [62] found that long-chain alkyl halides such as n-octadecyl chloride, n-hexadecyl bromide and n-hexdecyl iodide at temperatures above their melting points gave stick-slip sliding on steel, which is to be expected of the chemically unreactive type of halogen in these compounds. Compounds such as... 

The corresponding cyclic ion can be observed at m/e =135 and 137 in the mass spectrum of 1-bromohexane and at m/e = 105 and 107 in the mass spectrum of 2-chloroheptane. Such fragmentation is important only in the mass spectra of long-chain alkyl chlorides and bromides. 

Nishioka et al. (1960) observed that the degree of isotacticity depended on the organic radical in alkyl magnesium bromides. Branched and long-chain alkyl groups gave high isotacticity,... 

Heteroaromatic ammonium salts (one R stands for a long-chain alkyl group, and the remaining three R are components of an aromatic system such as pyridine, quinoline or isoquinoline), e.g. cetylpyridinium halide and alkylisoquinolinium bromide. 

As shown in a model study (Fig. 60), extension of the Barbier procedure to carboxylic acids is unsatisfactory for ketone synthesis. On the other hand, lithium carboxylates and lithium and alkyl chlorides lead to good to excellent yields when sonicated in THF. An application of such a procedure to the preparation of long chain alkyl ketones is given in Ch. 9, p. 361. The use of chlorides is required. The reason seems to be the necessity of a rapid formation of the organometallic (p. 217). When this formation is slow, with bromides or iodides, complex electron transfers take place and imexpected couplings result. 

The thermodynamic parameters change almost linearly with the total number of carbon atoms in hydrocarbon chains. The enthalpy increments for transitions are comparable with those for homologous series of n-alkanes, sodium alkyl sulfates, and long-chain alkyltrimethylammonium bromides [22,29-32,66,67], while the entropy change of melting falls within the range of those for stable bilayers of all double-chain amphiphiles, including natural lipids [19],... 

In the presence of thiazolium salts, aldehydes undergo conversion into a-hydroxy-ketones. An example of this process is the conversion of two molecules of butanal into 5-hydroxy-4-octanone. The catalyst is A-dodecylthiazolium bromide, which contains a long-chain alkyl substituent to improve its solubility in organic solvents. 

Currently available BAS include cholestyramine, colestipol and colesevelam hydrochloride (colestimide). Cholestyramine comprises a long-chain polymer of styrene with divinylbenzene trimethylbenzylammonium groups, whereas colestipol is a long-chain polymer of l-chloro-2,3-epoxypropane with diethylenetriamine. Colesevelam HCl is poly(allylamine hydrochloride) cross-linked with epichlorohydrin and alkylated with 1-bromodecane and 6-bromo-hexyl-trimethylammonium bromide. Bile-acid binding is enhanced and stabilised in the latter compound by long hydrophobic sidechains, increased density of primary amines, and quaternary amine sidechains. For this reason, colesevelam HCl exhibits increased affinity, specificity and capacity to bind bile acids compared with the other BAS. Colesevelam HCl also binds dihydroxy and trihydroxy bile acids with equal affinity, contrasting with cholestyramine and colestipol that preferentially bind dihydroxy bile acids (CDCA and deoxycholic acid). The latter BAS can lead to an imbalance towards trihydroxy bile acids and a more hydrophilic bile-acid pool. 

A better method for studying the alkali metal cation-soap anion interaction on the surface, according to Weil (58), is to assume a similarity between surface behavior and solution behavior and to use the activity coefficient of the solute in the solution as the parameter to account for surface behavior. By plotting activity coefficients as a function of the molality for the salts of the alkali metals (7, 26), the resulting order of the curves of the weak acids (formates, acetates, hydroxides) is the reverse of that found for the strong acids (chlorides, bromides, nitrates, chlorates, sulfates). The activity curves of the acetate salts can be used as the counterparts for the long-chain fatty acid salts, while those for the chlorides can be the analogs of the alkyl sulfates. The scheme is speculative in that the fatty acid and alkyl sulfate salts micellize, and acetate and chloride do not. 

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