Halide ion reactions

Intermediates have been trapped by distal attack of halide ion. Reaction of the a,3-unsaturated oxime (35) with PCls gave a good yield of A -phenyl-3-chloropropionamide (equation 21). Similar reactivity was observed with the alkynic oxime (36 equation 22). ... 

Speranza and Peppel, reported the synthesis of polyoxazolidones from diisocyanates and diepoxides using quarternary ammonium halides as catalysts (Reaction 1). They postulated that the opening of the epoxide ring, by halide ion (Reaction 2), preceded the addition of the isocyanate reaction ... 

The summation appears to be that halide ion reactions need much further study. The only reaction which has been studied kinetically is that of DPA with chloride ion, a reaction which follows the half-regeneration pathway, leading eventually to dichloro-DPA (43). In contrast, incidentally, DPA " and bromide ion undergo exclusive electron exchange (23). 

The formation of halatefV) and halide ions by reaction (11.4) is favoured by the use of hot concentrated solutions of alkali and an excess of the halogen. 

Partial but not complete loss of optical activity m S l reactions probably results from the carbocation not being completely free when it is attacked by the nucleophile Ionization of the alkyl halide gives a carbocation-hahde ion pair as depicted m Figure 8 8 The halide ion shields one side of the carbocation and the nucleophile captures the carbocation faster from the opposite side More product of inverted configuration is formed than product of retained configuration In spite of the observation that the products of S l reactions are only partially racemic the fact that these reactions are not stereospecific is more consistent with a carbocation intermediate than a concerted bimolecular mechanism... 

When formulating a mechanism for the reaction of alkynes with hydrogen halides we could propose a process analogous to that of electrophilic addition to alkenes m which the first step is formation of a carbocation and is rate determining The second step according to such a mechanism would be nucleophilic capture of the carbocation by a halide ion... 

Nucleophilic aliphatic substitution (Chapter 8) Reaction m which a nucleophile replaces a leaving group usually a halide ion from sp hybridized carbon Nucleophilic aliphatic substitution may proceed by either an S l or an Sfj2 mechanism... 

Halex reaction Halfan [36167-63-2] Half-life data Half-lives Halftones Halide glasses Halide ions Halides... 

The acid-catalyzed additions of bromide and chloride ion to thiiranes occurs readily, with halide preferentially but not exclusively attacking the most substituted carbon atom of the thiirane. The reaction of 1-substituted thiiranes with acetyl chloride shows a slight preference for halide attack at the less substituted carbon atom (80MI50601). For further discussion of electrophilic catalysis of halide ion attack see Section 5.06.3.3.2. The reaction of halogens with thiiranes involves electrophilic attack on sulfur (Section 5.06.3.3.6) followed by nucleophilic attack of halide ion on carbon. 

When halide ions or anions such as thiocyanate or azide are present, these anions are incorporated into the organic radical generated by decomposition of the peroxide. This anion transfer presumably occurs in the same step as the redox interaction with Cu(II), and such reactions have been called ligand-transfer reactions. " ... 

The reaction of chlorodifluorotnethane with alkoxide ions generated in low concentration from halide ions and epoxides [28, 29] is an interesting, higher temperature method that gives good to excellent yields of gem-difluorocyclo-propanes from just moderately nucleophilic olefins (equation 9)... 

With primary alcohols, the next stage is an Sn2 reaction in which the halide ion, bromide, for exfflnple, displaces a molecule of water from the alkyloxonium ion. 

Despite this, they are good solvents for chloride-ion transfer reactions, and solvo-acid-solvo-base reactions (p. 827) can be followed conductimetri-cally, voltametrically or by use of coloured indicators. As expected from their constitution, the trihalides of As and Sb are only feeble electron-pair donors (p. 198) but they have marked acceptor properties, particularly towards halide ions (p. 564) and amines. 

The trihalides of As, Sb and Bi are strong halide-ion acceptors and numerous complexes have been isolated with a wide variety of compositions. They are usually prepared by direct reaction of the trihalide with the appropriate... 

B (11— 12— 14). Examination of a more recent study suggests the von Richter reaction probably involves simultaneous attack of the triple bond on the diazo group accompanied by attack by a halide ion but not by a water molecule. The halocinnoline 13 is then hydrolyzed under the von Richter reaction conditions to furnish the 4-hydroxycinnoline derivative 14 (11 - 12- 13 14, pathway A). 

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