Chloromethyl groups

Chloromethjlation Reactions. The introduction of the chloromethyl group to both aHphatic and aromatic compounds is carried out by reaction of paraformaldehyde [30525-89-4] and hydrogen chloride. This method is used for synthesizing methyl chloromethyl ether [107-30-2], benzyl chloride [100-44-7], and chloromethyl acetate. 

Weak Base Anion Exchangers. Both styreoic and acryHc copolymers can be converted to weak base anion-exchange resias, but differeat syathetic routes are aecessary. Styreae—DVB copolymers are chloromethylated and aminated ia a two-step process. Chloromethyl groups are attached to the aromatic rings (5) by reactioa of chloromethyl methyl ether [107-30-2] CH2OCH2CI, with the copolymer ia the preseace of a Friedel-Crafts catalyst such as aluminum chloride [7446-70-0], AlCl, iroa(III) chloride [7705-08-0], FeCl, or ziac chloride [7646-85-7], ZaCl. ... 

Epichlorohydrin. Commercial polyester elastomers include both the homopolymer and the copolymer of epichl orohydrin with ethylene oxide. The very polar chloromethyl groups create basic resistance to oil for these polymers, and they have been extensively used in fuel lines however, the desire for lower fuel permeation is causing a search to be made for other polymers (10) (see Elastomers, synthetic-polyethers). 

The epoxidation is generally conducted in two steps (/) the polyol is added to epichlorohydrin in the presence of a Lewis acid catalyst (stannic chloride, boron triduoride) to produce the chlorohydrin intermediate, and (2) the intermediate is dehydrohalogenated with sodium hydroxide to yield the aliphatic glycidyl ether. A prominent side-reaction is the conversion of aliphatic hydroxyl groups (formed by the initial reaction) into chloromethyl groups by epichlorohydrin. The aliphatic glycidyl ether resins are used as flexibilizers for aromatic resins and as reactive diluents to reduce viscosities in resin systems. 

The reactivity of the chloromethyl group is illustrated by the reaction of 2,5-dimethyl-3,4-dichloromethylthiophene (174) with water, which gives (175) Another example of ether formation, is the formation of (176) upon normal acidic workup of the reaction product from 2-thiophenemagnesium bromide and 2-thiophenaldehyde. With... 

It is only recently that the chloromethylation reaction, well known in the benzene series, has been extended to isoxazoles. It has been thereby found that this reaction results in 4-chloromethyl derivatives (69), their yield decreasing as follows 5-phenyl > 3,5-dimethyl > 5-methyl > 3-methyl isoxazoles > isoxazole. To prove the position of the chloromethyl group these compounds were oxidized to the known isoxazole-4-carboxylic acids (70). It is especially noteworthy that pyridine and its homologs do not undergo chloromethylation. 

The introduction of a chloromethyl group on aromatic compounds (e.g. benzene 1) by reaction with formaldehyde 2 and gaseous hydrogen chloride in the presence of a catalyst is called the Blanc reaction ... 

The syntheses of these initiators is described in Sect. II.C. According to detailed H1 NMR analysis hydrosilylation yielded 15-20% isomers along with the major products 1, 2, and 3 as shown in Figs. 1-3. The presence of the isomers, listed in Table 1, should not affect initiating efficiency by the benzyl chloride group, in view of the structure and virtually identical H1 NMR chemical shifts of the chloromethyl groups. 

Finally, a series of 2-chloromethyl-5-aryl-1,3,4-oxadiazoles 82 were prepared by reaction of aromatic hydrazides 81 and a chloromethylorthofor-mate used as the solvent under microwave activation [62]. Potentially, the chloromethyl group could imdergo nucleophiUc substitution expanding the scope of this reaction (Scheme 28). 

Naphthalene dioxygenase from P. putida strain FI is able to oxidize a number of haloge-nated ethenes, propenes, and butenes, and d5 -hept-2-ene and cis-oct-2-ene (Lange and Wackett 1997). Alkenes with halogen and methyl substituents at double bonds form allyl alcohols, whereas those with only alkyl or chloromethyl groups form diols. 

Coumarincarboxylate derivatives are versatile, efficient, low molecular weight, nonpeptidic protease inhibitors. Both esters and amides behave as time-dependent inhibitors of a-chymotrypsin but the esters are clearly more efficient than the corresponding amides. The criteria for a suicide mechanism are met. The presence of a latent alkylating function at the 6-position (chloromethyl group) is required to produce to inactivation by a suicide mechanism (Scheme 11.3, pathway a). Aryl esters, in particular the meta-substituted phenyl esters are the best inhibitors. Thus, m-chlorophenyl 6-(chloromethyl)-2-oxo-27/-l-benzopyran-3-carboxylate is one of the well-known inactivator of a-chymotrypsin (kJK, = 76(),000M s 1 at pH 7.5 and 25 °C, Table 11.1). 

Poly(epichlorohydrin) (PECH) and poly(2,6 - dimethyl-1,4-phenylene oxide) (PPO) containing pendant mesogenic units separated form the main chain through spacers of zero to ten methylene units were synthesized and characterized in order to test the "spacer concept." Both polymers were modified by phase transfer catalyzed esterifications of the chloromethyl groups (PECH) or the bromobenzyl groups (brominated PPO) with potassium co -(4-oxybiphenyl) alkanoates and potassium u-(4-methoxy-4-oxybiphenyl)-alk.an oates. While PPO required ten methylene units as a spacer and 4,4 -methoxybiphenyl as mesogen to present thermotropic liquid crystalline mesomorphism,... 

PECH was modified under similar reaction conditions, except that dimethylformamide (DMF) was used as the reaction solvent. In addition, the phase-transfer-catalyzed etherification of the chloromethyl groups of PECH with sodium 4-methoxy -4 -biphenoxide was used to synthesize PECH with direct attachment of the mesogen to the polymer backbone. Similar notations to those used to describe the functionalized PPO are used for functionalized PECH. In this last case, PPO was replaced with PECH. Esterification routes of both PPO and PECH are presented in Scheme I. 

Bromobenzyl groups were introduced into PPO by radical bromination of the methyl groups. The PPO bromobenzyl groups and PECH chloromethyl groups were then esterified under phase-transfer-catalyzed reaction conditions with the potassium carboxylates just described. This procedure has been described previously (29). The sodium salt of 4-methoxy-4 -hydroxybiphenyl was also reacted with PECH (no spacer). 

Proteins may be covalently attached to the latex particle by a reaction of the chloromethyl group with a-amino groups of lysine residues. We studied this process (17) using bovine serum albumin as a model protein - the reaction is of considerable interest because latex-bound antigens or antibodies may be used for highly sensitive immunoassays. The temperature dependence of the rate of protein attachment to the latex particle was unusually small - this rate increased only by 27% when the temperature was raised from 25°C to 35°C. This suggests that non-covalent protein adsorption on the polymer is rate determining. On the other hand. the rate of chloride release increases in this temperature interval by a factor of 17 and while the protein is bound to the latex particle by only 2 bonds at 25°C, 22 bonds are formed at 35°C. 

In a similar way, piperazinone derivatives can be prepared by either addition of the formed amine to a carboxylate moiety or by an intramolecular alkylation with a chloromethyl group present in the substrate [485]. 

The carbonylation reaction of the gem-dibromocyclopropanes 159 bearing the chloromethyl group leads via ring-opening to the 7, d-unsaturated carboxylic... 

The principles needed to design a polymer of low flammability are reasonably well understood and have been systematized by Van Krevelen (5). A number of methods have been found for modifying the structure of an inherently flammable polymer to make it respond better to conventional flame retardant systems. For example, extensive work by Pearce et al. at Polytechnic (38, 39) has demonstrated that incorporation of certain ring systems such as phthalide or fluorenone structures into a polymer can greatly increase char and thus flame resistance. Pearce, et al. also showed that increased char formation from polystyrene could be achieved by the introduction of chloromethyl groups on the aromatic rings, along with the addition of antimony oxide or zinc oxide to provide a latent Friedel-Crafts catalyst. 

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