Acetyl halides

Yamase and Goto406 determined first- and second-order rate coefficients for the aluminium chloride-catalysed reaction of halide derivatives of benzoic acid (lO5 = F, 1.73 Cl, 4.49 Br, 4.35 I, 0.81) and phenylacetic acid (105fc2 = F, 12 Cl, 21 Br, 9 I, 6) with benzene. The maxima in the rates for the acid chloride are best accommodated by the assumption that a highly (but not completely) polarised complex takes part in the transition state. Polarisation of such a complex would be aided by electron supply, and consistently, the acetyl halides are about a hundred times as reactive as the benzoyl compounds (see p. 180, also Tables 105 and 108). 

Formally, they can all be viewed as derivatives of hydroxylamine, H2N—OH indeed, oximes can be prepared by the addition of hydroxylamine to aldehydes and ketones (equations 1 and 2), and hydroxamic acids by its reactions with acetyl halides and esters (equations 3 and 4). ... 

The living cationic ring opening polymerization (CROP) of 2-oxazolines was first reported in the 1960s [61, 62]. The polymerization can be initiated by an electrophile such as benzyl halides, acetyl halides, and tosylate or triflate derivatives. The typical polymerization mechanism for 2-alkyl-2-oxazoline initiated by methyl tosylate is shown in Scheme 6. 

For instance, the CROP of EtOx using four different acetyl halide type of initiators showed that the rate of polymerization increases with the decreased basicity of the counter ion acetyl iodide < acetyl bromide < acetyl chloride. The apparent rates of polymerization of EtOx with different initiators are listed in Table 2. 

Paulus RM, Becer CR, Hoogenboom R et al. (2008) Acetyl halide initiator screening for the cationic ring opening polymerization of 2-ethyl-2-oxazoline. Macromol Chem Phys 209 794-800... 

Zirconium and hafnium tetraalkoxides are highly reactive compounds. They react with water, alcohols, silanols, hydrogen halides, acetyl halides, certain Lewis bases, aryl isocyanates and other metal alkoxides. With chelating hydroxylic compounds HL, such as j8-diketones, carboxylic acids and Schiff bases, they give complexes of the type ML (OR)4 these reactions are discussed in the sections dealing with the chelating ligand. 

Note, however, that the comparison is with measurements for the benzoyl halides in a more aqueous medium than the acetyl halides and that this would favour a greater contribution from the unimolecular mechanism in the benzoyl halides. 

The reaction of propylene sulfide or 3-chlon>propyl Qe sulfide with acetyl halides or hydrogen halides leads to good yields of the 2-halo-alhyl compound (LXXH) which results from cleavage of the seconds) y... 

Highly fluorinated ethenes react readily with oxygen to yield epoxides, polymeric peroxides, perfluorocyclopropane, and, by rearrangement, fluorinated acetyl halides carbonyl fluoride and carbon dioxide are undesired byproducts, the amount of which is dependent on the method used. 

Again there are numerous reports on the synthesis of methylenefurans. The reaction of acetals with 2-(trimethylsilyloxymethyl)allyltrimethylsilane 71 under the influence of tin(II)halide and acetyl halide afforded 2-suhstituted 4-methylenetetrahydrofurans in good yields. 

The following step could be the reductive elimination of the acetyl halide to react with methanol. The growth of IR bands in the 1710-1685 cm- domain might be interpreted as due to CH COI accumulation and possibly further reaction with substrates present in the medium. Nevertheless readdition of CO restored the monovalent rhodium dicarbonyl thus indicative that somehow CH COI was eliminated. 

The reaction between a phosphonium ylidc derived from a fluorotrihalomcthane and an acetyl halide leads to the ylide acylation product 9 and the salt 10 by the Wittig reaction. This has been used to obtain alkenes 11 from acyl halides. ... 

Monoalkyl acetyl halides, RCHjCOX, are converted to aldoketene dimers. These materials are useful in the synthesis of /3-keto acid derivatives. ... 

While the first two allow the isolation of the reaction products, the third does not. When a Lewis acid is mixed with an acyl halide, a donor-acceptor complex RCOX. .. MtX , or full ionisation by halide ion transfer, to give RCO MtX +i, or both, take place. The extent of ionisation depends mostly on the nature and strength of the Lewis acid used Thus, for example, acetyl halides react with stannic chloride and titanium tetrachloride to give mostly the coordination complex while with antimony pentachloride, pen-tafluoride and boron fluoride they give the conesponding acylium salts. Many of these... 

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