Abnormal addition

Hydrogen hahdes normally add to form 1,2-dihaLides, though an abnormal addition of hydrogen bromide is known, leading to 3-bromo-l-chloropropane [109-70-6], the reaction is beUeved to proceed by a free-radical mechanism. Water can be added by treatment with sulfuric acid at ambient or lower temperatures, followed by dilution with water. The product is l-chloro-2-propanol [127-00-4]. 

Abnormal addition of epichlorohydrin, ie, addition to the mote substituted carbon atom ... 

The tendency for radicals to give tail addition means that a head-to-head linkage will, most likely, be followed by a tail-to-tail linkage (Scheme 4.5). Thus, head-to-head linkages formed by an "abnormal" addition reaction are chemically distinct from those formed in termination by combination of propagating radicals (Scheme 4.6). 

Scheme 4 Normal and abnormal addition of nucleophiles to sulfenes...

However, King et al. (1977) have shown that in some cases one can get abnormal addition and the formation of substituted sulfinic acids (Scheme 4). Abnormal addition, for example, is involved as the first step in the complex pathway (207) by which sulfine [90] is formed from PhCH=S02 when phenylmethanesulfonyl chloride is treated with a tertiary amine in the absence of any of the normal sulfene-trapping reagents (King and Harding, 1976). 

The reaction of benzothiazole (386a) with DMAD has been shown to give a mixture of products consisting of 513 (34%) and 387 (small amounts). However, Ogura and co-workers have reported that benzothiazole reacts with DMAD to give a mixture of the initial addition product 387 and an abnormal addition product 514 (Scheme 82). 

Rationalization of these facts appear to require an abnormal addition. It has been proposed (39) that a free-radical adds to thiocarbonyl fluoride first to give... 

The radical chain mechanism for the abnormal addition of thiols and hydrogen sulfide (contrary to MarkOwnikofF s rule) is of great practical... 

Addition of HBr in nonpolar solvents to terminal alkenes was found to give anti-Markovnikov products even under nonradical conditions.122 Products formed in both the normal and abnormal additions may be obtained in near-quantitative yields by changing the temperature and the reagent reactant ratio 122... 

Important related studies have been published by House, tJ- u and by Naqvi end co-workers,1218 on the subject of magnesium bromide-initiated epoxide isomerization. Their results, discussed in section IV.2.A, suggest that abnormal addition of Qrignard reagents to dicyelio a-haloketones does not proceed by way of an ephemeral poxide intermediate, in accordance with the view expressed previously by Gciesman and Akawie.4 4... 

The ionic addition of hydrogen bromide was discussed in Section 10-4 and will not be considered further at this point. Two questions with regard to the so-called abnormal addition will be given special attention. Why does the radical mechanism give a product of different structure than the ionic addition Why does the radical addition occur readily with hydrogen bromide but rarely with the other hydrogen halides (See Exercise 10-25.)... 

The abnormal addition of hydrogen bromide is catalyzed strongly by peroxides, which have the structure R—O—O—R and decompose thermally to give RO- radicals (see Section 4-5B) ... 

Vaughan et al. (103) studied the photobromination of ethylene, propylene, 1-butene, isobutene, and vinyl chloride in the gas phase and found in every case where a distinction could be made that the product was almost entirely the so-called abnormal addition product in terms of the Markownikoff s rule. However, the more recent work of Skell et al. (95) shows that 2-bromo-w-propyl radical may rearrange very rapidly to 1-bromo-isopropyl radical. In view of this the observed exclusive terminal addition of Br atoms in the case of propylene could be in part due to rapid rearrangement. 

If the addition of a monomer to the growing chain takes place in more than one way, then the "abnormal addition, i.e. that which does not take place in the usual propagation step, might lead to termination. For example, Sela and Berger (48) assume that the anionic polymerization of Leuch s anhydride is terminated by the abnormal additions which yields carboxylate ions instead of imide ions ... 

Eqnations (14) and (15) were derived on the assumption that a 1,2-glycol stmctnre will result from every abnormal monomer addition. What is the result of two successive abnormal additions Can yon derive a modified expression on the assumption that the probability of an abnormal addition is independent of all previous additions Would such an assumption be reasonable Are your experimental resnlts (or indeed those of Flory and Leutner) precise enough to make such a modification significant in experimental terms What polymerization factors besides temperatnre might inflnence the freqnency of abnormal head-to-head linkages ... 

BETA-BLOCKERS DILTIAZEM t hypotensive and bradycardic effects cases of severe bradycardia and AV block when both drugs are administered concurrently in the presence of pre-existing heart failure or conduction abnormalities Additive effects on conduction diltiazem causes bradycardia, sinoatrial block and AV block. Also, diltiazem inhibits CYP1A2-mediated metabolism of propanolol Monitor PR, BP and ECG at least weekly until stable. Warn patients to report symptoms of hypotension (light-headedness, dizziness on standing, etc.)... 

Observations on this system may not apply to other catalyst systems but the fact that abnormal addition of propene has been demonstrated in elastomeric E/P copolymers prepared under very different conditions makes it clear that, at the least, the values of and rj are approximations. It would be of interest to calculate (assuming, for example, that the ratio of the fractions of head-to-head and head-to-tail units equals the ratio of the corresponding rate coefficients) what differences from the true rj and T2 ratios would result from the occurrence of 5—10% of abnormal addition. 

In cases where Z is small—which makes steric considerations less important—and is less able to stabilize the growing end of the chain by electron delocalization, some head-to-head addition and some tail-to-tail addition also occur. This has been observed primarily in situations where Z is fluorine. Abnormal addition, however, has never been found to constitute more than 10% of the overall chain. 

It further emphasizes the point that ammonium salts are only hydrogen compounds where the hydrogen atom has associated with one ammonia, while if it has associated with it more ammonia molecules it is generally considered as an abnormal addition compound. Ammonium salts are only one particular case of ammoniated hydrogen compounds. Similarly, oxonium salts are only a particular case of the series of hydrates of hydrogen and similar compounds. 

The normal addition is catalyzed by acids or bases and yields branched products, whereas the abnormal addition is free radical catalyzed and gives linear products. Activated double bonds as in the case of methyl acrylate give the same product by both routes, but different mechanisms are said to be operative [74]. 

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