From haloform reaction

PROBABLE FATE photolysis, could be important, only identifiable transformation process if released to air is reaction with hydroxyl radicals with an estimated half-life of 8.4 months oxidation, has a possibility of occurring, photooxidation half-life in air 42.7 days-1.2 yrs hydroiysis too slow to be important, first-order hydrolytic half-life 275 yrs voiatilization likely to be a significant transport process, if released to water or soil, volatilization will be the dominant environmental fate process, volatilization half-life from rivers and streams 43 min-16.6 days with a typical half-life being 46 hrs sorption adsorption onto activated carbon has been demonstrated bioiogicai processes moderate potential for bioaccumulation, biodegradation occurs in some organisms, in aquatic media where volatilization is not possible, anaerobic degradation may be the major removal process other reactions/interactions may be formed from haloform reaction after chlorination of water if sufficient bromide is present... 

The haloform reaction is sometimes used for the preparation of carboxylic acids from methyl ketones... 

Fluorine cannot be used, although trifluoroketones can be cleaved into carboxylate and trifluoromethane. The haloform reaction can be conducted under mild conditions—at temperatures ranging from 0-10 °C—in good yields even a sensitive starting material like methylvinylketone can be converted into acrylic acid in good yield. 

More useful for synthetic purposes, however, is the combination of the zinc-copper couple with methylene iodide to generate carbene-zinc iodide complex, which undergoes addition to double bonds exclusively to form cyclopropanes (7). The base-catalyzed generation of halocarbenes from haloforms (2) also provides a general route to 1,1-dihalocyclopropanes via carbene addition, as does the nonbasic generation of dihalocarbenes from phenyl(trihalomethyl)mercury compounds. Details of these reactions are given below. 

Figure 11-9 illustrates the mechanism for the haloform reaction. The mechanism involves a repeated series of base attacks (removal of an a-hydrogen) followed by the reaction with the halogen until all three a-hydrogen atoms are replaced. Then the base attacks the carbonyl carbon to induce the loss of a carbanion Q.CXf. The highly reactive carbanion quickly attacks and removes the hydrogen from the carboxylic acid group. 

Haloform reaction, 237, 296 Halogenation alkanes, 300, 323 alkenes, 179,186, 313 benzene, 138,316 ketones, 295 Hammett equation, 362 additional parameters, 374, 388, 395 derivation of, 362 deviations from, 375 empirical nature of, 395 implications of, 394 reaction pathway, and, 375 solvent effects and, 388 spectroscopic correlations, 392 standard reaction for, 362, 395 steric effects and, 361, 383 thermodynamic implications of, 394 Hammett plots, 359 change in rate-limiting step and, 383 change in reaction pathway and, 378... 

Problem 16.8 (a) Why isn t 2-naphthoic acid made from 2-chloronaphthalene (f>) How is 2-naphthoic acid prepared in a haloform reaction M... 

Apparently the only previous case of the isolation of a chlorinated acid from a haloform reaction is that reported by Arnold et al. [8], who acidified the reaction mixture before decomposition of the excess hypochlorite. (Even though we decomposed the excess hypochlorite before acidification, the unchlorinated acid was not obtained.) These authors [8] also obtained an ester as the product of the haloform reaction. It seems likely that conditions for performing the haloform reaction can be found which will make the one-step conversion of a methyl ketone to the ester of the corresponding acid a general reaction. ... 

The synthesis of a pyrrole segment common to netropsin and distamycin is shown in Scheme 2ji°l Friedel-Crafts acylation of 1-methylpyrrole (1) followed by nitration at C4 provides 3 in 54% yield. After a haloform reaction, hydrogenolysis, N-protection with B0C2O, and saponification, the pyrrolecarboxylic derivative acid 7 was obtained in 30% overall yield from 3. This monomer is readily chain-extended to the pyrrole-imidazole derivative 9 (Scheme 3)J10 Furthermore, solid-phase synthesis with this and related pyrrole-containing building blocks leads to polyamides that have recently been used in the recognition of a 16 base-pair sequence in the minor groove of DNA.1" ... 

Because the haloform reaction is fast, in some cases it can be used to prepare unsaturated acids from unsaturated ketones without serious complications caused by addition of halogen to the double bond ... 

To retain a side-chain substituent, selective methods of oxidation are required. For example, 4-methylbenzoic acid can be prepared from l-(4-methylphenyl)-ethanone by the haloform reaction (Section 17-2B) ... 

The use of the haloform reaction for the conversion of methyl ketones into carboxylic acids (Sections 5.11.1, p. 667) is also applicable in the aromatic field. The conditions may be readily adapted from those described for the conversion of aliphatic methyl ketones into carboxylic acids (Expt 5.124). 

The formation of dihalocarbene is one of the most useful phase-transfer processes developed in organic chemistry. The dihalocarbenes, once generated from haloform and base, can undergo addition or insertion reactions (3, 11, 12). If the double bond is complexed to a metal, addition by the carbene will not occur, but rather insertion into a saturated carbon-hydrogen bond will take place. 

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