Chlorobutyl

Acetyl chlotide is reduced by vatious organometaUic compounds, eg, LiAlH (18). / fZ-Butyl alcohol lessens the activity of LiAlH to form lithium tti-/-butoxyalumium hydtide [17476-04-9] C22H2gA102Li, which can convert acetyl chlotide to acetaldehyde [75-07-0] (19). Triphenyl tin hydtide also reduces acetyl chlotide (20). Acetyl chlotide in the presence of Pt(II) or Rh(I) complexes, can cleave tetrahydrofuran [109-99-9] C HgO, to form chlorobutyl acetate [13398-04-4] in about 72% yield (21). Although catalytic hydrogenation of acetyl chlotide in the Rosenmund reaction is not very satisfactory, it is catalyticaHy possible to reduce acetic anhydride to ethylidene diacetate [542-10-9] in the presence of acetyl chlotide over palladium complexes (22). Rhodium trichloride, methyl iodide, and ttiphenylphosphine combine into a complex that is active in reducing acetyl chlotide (23). 

Halobutyl Cures. Halogenated butyls cure faster in sulfur-accelerator systems than butyl bromobutyl is generally faster than chlorobutyl. Zinc oxide-based cure systems result in C—C bonds formed by alkylation through dehydrohalogenation of the halobutyl to form a zinc chloride catalyst (94,95). Cure rate is increased by stearic acid, but there is a competitive reaction of substitution at the halogen site. Because of this, stearic acid can reduce the overall state of cure (number of cross-links). Water is a strong retarder because it forms complexes with the reactive intermediates. Amine cure may be represented as follows ... 

Polyisobutylene and isobutylene—isoprene copolymers are considered to have no chronic hazard associated with exposure under normal industrial use. Some grades can be used in chewing-gum base, and are regulated by the PDA in 21 CPR 172.615. Vulcanized products prepared from butyl mbber or halogenated butyl mbber contain small amounts of toxic materials as a result of the particular vulcanization chemistry. Although many vulcanizates are inert, eg, zinc oxide cured chlorobutyl is used extensively in pharmaceutical stoppers, specific recommendations should be sought from suppHers. 

Chlorobutyl rubber is prepared by chlorination of butyl rubber (chlorine content is about 1 wt%). This is a substitution reaction produced at the allylic position, so little carbon-carbon double unsaturation is lost. Therefore, chlorobutyl rubber has enhanced reactivity of the carbon-carbon double bonds and supplies additional reactive sites for cross-linking. Furthermore, enhanced adhesion is obtained to polar substrates and it can be blended with other, more unsaturated elastomers. 

Halobutyl Chlorobutyl Chloroiso- butene- isoprene CIIR... 

With Freon 112 or 113 as a solvent, fluonnation of pnmary butyl halides with bromine trifluonde can give mixtures of primary and secondary fluorides When 1,4 dibromobutane is the substrate, 93% l-bromo-4-fluorobutane and 1% 1-bro-mo-3-fluorobutane is obtained, with 1,4 dichlorobutane, the product contains 65% l-chloro-3-fluorobutane and 35% 1-chloro 4 fluorobutane When 4-bromo- or 4-chlorobutyl trifluoroacetate is used, the ratio of 4-fluorobutyl tnfluoroacetate to 3 fluorobutyl trifluoroacetate is 1 4 The effect of solvent is measured in another set of experiments When the reaction of bromine trifluonde and l,3-dichloro-2-fluoropropane in either Freon 113 or hydrogen fluoride is allowed to proceed to 40% conversion, the product mixture has the composition shown m Table 1 [/O] When 1 chloro 2,3-dibromopropane is combined with one-third of a mole of bromine trifluonde, both 1 bromo 3 chloro-2-fluoropropane and l-chloro-2,3-di-fluoropropane are formed [//] (equation 10)... 

Treatment of bis-lactim ether 420 with BuLi, then with cw-l,4-dichloro-2-butene in the presence of Nal afforded 3,4,9,9n-tetrahydro-6//-pyrido[l,2-fl]pyrazin-4-one (421) with 96% diastereomeric excess (97TA1855). Reaction of l,2-diphenyl-6-methyl-quinoxaline with 1,4-dichlorobutane in THF in the presence of Na at —78°C afforded a 3 1 mixture of 4a,5-diphenyl-9-methyl-l,2,3,4-tetrahydro-4a//-pyrido[l,2-n]quinoxaline and 4-(4-chlorobutyl)-2,3-diphenyl-6-methyl-1,4-dihydroquinoxaline (98JHC1349). 

C) 4 -lodobutyl-3,4-Dimethoxybenzoate 32.5 g of 4 -chlorobutyl-3,4-dimethoxybenzoate and 19.5 g of sodium iodide (10% excess) were boiled in 150 ml of methyl ethyl ketone for 2.5 hours after cooling and filtering off the sodium chloride produced, the reaction was found not to be entirely completed boiling was then continued for another two hours the reaction mixture was cooled, and the solid filtered off and washed with 2 x 100 ml of ether. 

Chlorobutyl CIIR poor with oils, solvents etc. ... 

Besides simple alkyl-substituted sulfoxides, (a-chloroalkyl)sulfoxides have been used as reagents for diastereoselective addition reactions. Thus, a synthesis of enantiomerically pure 2-hydroxy carboxylates is based on the addition of (-)-l-[(l-chlorobutyl)sulfinyl]-4-methyl-benzene (10) to aldehydes433. The sulfoxide, optically pure with respect to the sulfoxide chirality but a mixture of diastereomers with respect to the a-sulfinyl carbon, can be readily deprotonated at — 55 °C. Subsequent addition to aldehydes afforded a mixture of the diastereomers 11A and 11B. Although the diastereoselectivity of the addition reaction is very low, the diastereomers are easily separated by flash chromatography. Thermal elimination of the sulfinyl group in refluxing xylene cleanly afforded the vinyl chlorides 12 A/12B in high chemical yield as a mixture of E- and Z-isomers. After ozonolysis in ethanol, followed by reductive workup, enantiomerically pure ethyl a-hydroxycarboxylates were obtained. 

C,7H, N20 93271-68-2) see Praziquantel l-cyclohexyl-5-(4-chlorobutyl)tetrazole (C, H C1N4 73963-42-5) see Cilostazol cyclohexylglyoxylic acid (CSH12O3 4354-49-8) see Cetiedil iV-cyclohexyl-AP-(2-hydroxyethyl)urea (C5HisN202 66929-46-2) see Lomustine... 

Figure 9.15 shows typical force curves for a chlorobutyl mbber (CUR) and a namral rubber (NR) sample. It is immediately obvious that the CIIR sample is softer and, as expected, shows much greater hysteresis and hence poorer resilience than the NR sample. 

FIGURE 9.15 Typical force curves on (a) chlorobutyl rubber (CIIR) and (b) natural rubber (NR) samples showing much greater hysteresis and hence poorer resibence for the CIER sample. (From Huson, M.G. and Maxwell, J.M., Polym. Test., 25, 2, 2006.)... 

FIGURE 9.18 (continued) (b) Resilience measurements of elastomers. Samples of chlorobutyl rubber (CIIR), polybutadiene rubber (BR), and cross-linked recombinant resilin. (From Elvin, C.M., Carr, A.G., Huson, M.G., Maxwell, J.M., Pearson, R.D., Vuocolol, T., Liyou, N.E., Wong, D.C.C., Merritt, D.J., and Dixon, N.E., Nature, 437, 999, 2005.)... 

Warrach and Tsou [115] reported that bis-(l,2,3,6-tetrahydrobenzaldehyde)-pentaerythrityl acetal provides superior ozone protection for polychloroprene, butyl rubber, chlorobutyl, and... 

The 8-branch point present in PECH is absent in polymers of higher 1,2-epoxy-u-chloroalkanes. Such polymers are readily prepared by treatment of the neat monomers with the modified tri-ethyl al uminum catalyst introduced by Vandenberg (5, ) results for (2-chloroethyl)oxirane, (3-chloropropyl)oxirane and (4-chlorobutyl)-oxirane (2a-c) are summarized in Table I (7, 8). 

Figure 1. Conversion versus time for substitution by tetrabutylammonium benzoate on poly(epichlorohydrin) (A, A, separate runs) poly[(2-chloroethyl)-oxirane] (O) poly[(3-chloropropyl)oxirane] (V) and poly[(4-chlorobutyl)-oxirane] ( ). (Reproduced with permission from ref. 1. Copyright 1982 Wiley.)...

Unstirred mixtures of sulfinyl chloride and tetrahydrofuran may react extremely exothermally and with gas evolution when heated to 60°C, the products of ring-scission being bis(4-chlorobutyl) ether, 1,4-dichlorobutane and sulfur dioxide. Some ratios of the two reactants enhance the tendency, and relatively confined mixtures may explode. Sufficient heat to initiate the reaction may arise from selfmixing of the layered liquids, the chloride being twice as dense as THF. 

Butyl rubber is not compatible with natural rubber, SBR, nitrile rubber or with any other elastomer having an appreciable degree of unsaturation modified butyls (chlorobutyl and bromobutyl) are compatible with such elastomers and used as liners in tubeless tyres to improve air retention. 

Chlorobutyl (CIIR) and bromobutyl (BIIR) are modified types containing 1.2% wt of chlorine or bromine, the isoprene unit being the site of halogenation. Introduction of the halogen gives greater cure flexibility, and enhanced cure compatibility in blends with other diene rubbers. It also confers increased adhesion to other rubbers and metals. 

Calcium stearate has to be added to stabilise the chlorobutyl during processing. 

The only example of this kind is the thermal isomerization of 1-cyanocyclopentyl-iminosulfur dichloride into 3-chloro-4-(4-chlorobutyl)-l,2,5-thiadiazole. The reaction has been previously reviewed in CHEC(1984) <1984CHEC(6)513, 1973JOU2522>. 

Biphenylyl)urea, 31,10 l-(4-Biphenylyl)urea, 31, 10 Bis-4-chlorobutyl ether, 37, 55 Bischi-oromethyl ether, 36,1... 

---