Chlorine substituents

Sucralose has the structure most similar to su crose Galactose replaces the glucose unit of sucrose and chlorines replace three of the hydroxyl groups Sucralose is the newest artificial sweetener having been approved by the U S Food and Drug Adminis tration in 1998 The three chlorine substituents do not dimmish sweetness but do interfere with the ability of the body to metabolize sucralose It there fore has no food value and IS noncaloric... 

Vinyhdene chloride polymeri2es by both ionic and free-radical reactions. Processes based on the latter are far more common (23). Vinyhdene chloride is of average reactivity when compared with other unsaturated monomers. The chlorine substituents stabih2e radicals in the intermediate state of an addition reaction. Because they are also strongly electron-withdrawing, they polari2e the double bond, making it susceptible to anionic attack. For the same reason, a carbonium ion intermediate is not favored. 

The monochlorotoluenes are stable to the action of steam, alkahes, amines, and hydrochloric and phosphoric acids at moderate temperatures and pressures. Three classes of reactions, those involving the aromatic ring, the methyl group, and the chlorine substituent, are known for monochlorotoluenes. 

Nearly all of the benzyl chloride [100-44-7], henzal chloride [98-87-3], and hen zotrichl oride /P< -(97-i manufactured is converted to other chemical intermediates or products by reactions involving the chlorine substituents of the side chain. Each of the compounds has a single primary use that consumes a large portion of the compound produced. Benzyl chloride is utilized in the manufacture of benzyl butyl phthalate, a vinyl resin plasticizer benzal chloride is hydrolyzed to benzaldehyde hen zotrichl oride is converted to benzoyl chloride. Benzyl chloride is also hydrolyzed to benzyl alcohol, which is used in the photographic industry, in perfumes (as esters), and in peptide synthesis by conversion to benzyl chloroformate [501-53-1] (see Benzyl ALCOHOL AND p-PHENETHYL ALCOHOL CARBONIC AND CARBONOCm ORIDIC ESTERS). 

Poly(hydroxyethyl methacrylate)-dye copolymers —The color additives formed by reaction of one or more of the foUowiag reactive dyes with poly(hydroxyethyl methacrylate), so that the sulfate group (or groups) or chlorine substituent of the dye is replaced by an ether linkage to poly(hydroxyethyl methacrylate) (see Dyes, reactive). The dyes that may be used alone or ia combination are... 

Deep fluorinalion of alkanes, ethers, acid fmlides, esters, alkyl chlorides, most ketones, ketals, orthoesters, and combinations of these functional groups produces principally the perfluonnated analogues (Table 2) Chlorine substituents (or chloro groups) usually survive fluorination... 

Auwers and others soon discovered that the transformation 3 —> 6 did not consistently give flavonols such as 2. For example, alcoholic alkali treatment of dibromide 11 produced 2-benzoyl-benzofuran-3-one 12 instead of the corresponding flavonol. The same observation was made by Robert Robinson in a failed attempt to make datiscetin in 19257 It has reported that when there is a meta (to the coumarone ring oxygen) substituent such as methyl or methoxy, flavonol formation is hindered, whereas methyl, methoxy, and chlorine substituents at the ortho and para positions are conducive to flavonol formation. ... 

A careful use of solvent effects should be of great assistance in synthetic chemistry. For example, it may be predicted from the solvent effects described above that in the reaction of 2,4-dichloroquinohne with piperidine the a y ratio should increase in the less polar solvents, although the result might be obscured by the mutual influence of the two chlorine substituents. Nitro-activated benzenes support this prediction since ortho para ratios of 4.2 in methanol and 69 in benzene were observed in the reaction of 2,4-dichloronitrobenzene with piperidine. ... 

Relative reactivity of ring-positions based on positional selectivity of polychloro-azines must be regarded with caution because of the unequal activating effects of the chlorine substituents on each other. Also, it should be emphasized that one cannot use the positional selectivity in di- and tri-substitutions to assess relative reactivity of different positions. In such substitutions, the reactivity is determined by a complex combination of activating and deactivating effects which are unequal at the ring-positions (cf. Sections II, E, 1, II, E, 2,c, and II,E,2,e). 

The limited data available for 2,4-dichloroquinoline (Table X, line 9) show a substantially greater rate of methoxylation than for the 2- and 4-chloro analogs (Table X, line 6 and Table XI, line 2), as a result of activation (lowering of E ) by the additional chlorine substituent. Unequal mutual activation (cf. Section III, B, 2) by these substituents is indicated by the rate ratio of 1.9 1 for 4- to 2-substi-tution in the dichloro compound and of 25 1 for the two mono-chloro compounds. 

The relations 4- > 2-position in rate and 4- < 2-position in will apparently apply to reactions with anions, but the reverse relation is observed in piperidination, presumably due to 2-substitution being favored by hydrogen bonding in the zwitterionic transition state (cf. 47, 59, and 277) or by solvent-assisted proton removal from the intermediate complex (235). Substitutions of polychloroquino-lines (in which there is a combined effect of azine-nitrogen and unequal mutual activation of the chlorine substituents) also show 4- > 2-position in reactivity contrary statements are documented by these same references. Examples are cited below of the relation 2- > 4-position when a protonated substrate or a cyclic transition state is involved. 

The way in which various substituents affect the polarization of a carbonyl group is similar to the way they affect the reactivity of an aromatic ring toward electrophilic substitution (Section 16.5). A chlorine substituent, for example, inductively withdraws electrons from an acyl group in the same way that it withdraws elections from and thus deactivates an aromatic ring. Similarly, amino, methoxvl, and methylthio substituents donate electrons to acyl groups by resonance in the same way that they donate electrons to and thus activate aromatic rings. 

The AfA/ -diacetylphenylhydrazine derivatives 2 are converted into 5,6-diacetyl-5,6-dihy-drodibenzo[ft,/][l,4,5]thiadiazepines 3 in the presence of potassium carbonate. (The reaction fails in the absence of the chlorine substituents.) Hydrolysis of the products 3 results in the tricyclic hydrazines 4, which are transformed quantitatively into dibenzothiadiazepines 5 in... 

The diastereoselectivity of the reactions of (Z)-l-methyl-2-butenylboronate is greater than that of (Z)-l-chloro-2-butenylboronate, evidently because the smaller, more electronegative chlorine substituent has a greater preference to orient in the axial position of transition state 5 than the methyl group. Excellent diastereoselectivity has also been observed in reactions of 1-methyl-3,3-disubstituted 2-propenylboronates and aldehydes27,40. 

More than twenty years ago, Nesmeyanov s group showed that chlorine can be substituted by a variety of nucleophiles in FeCp(r 6-PhCl)+ [83, 84]. Indeed the chlorine substituent in the chlorobenzene (even) ligand is 1000 times more reactive than when it is located on the cyclopentadienyl (odd) ligand [85]. The FeCp+ is a good withdrawing group which is equivalent to two nitro groups in terms of activation. The reactions proceed under ambient conditions with primary or secondary amines and have been extended to other substituted chloroarene complexes [86, 87] Eq. (22), Table 2. 

The most general reaction for the preparation of sulphoximines from sulphoxides is simply by reaction with hydrazoic acid (equation 65)178. Highly substituted sulphoxides, such as diethyl sulphoxide with more than two chlorine substituents, do not undergo reaction to form the sulphoximine in this way. 

Acyclic sulphones with a-chlorine substituents also produce sulphonic acid derivatives in good yields, although in these cases rearrangement occurs via a thiiren dioxide intermediate (equation 91)208. 

Figure 5. Carbon-chlorine bond lengths (A) of chlorinated dibenzo-p-dioxins as a function of the number of chlorine substituents.

In the case of alkylation using allylsilancs in the presence of aluminum chloride as a catalyst, allylsilanes containing one or more chlorine substituents on the silicon react with aromatic compounds at room temperature or below 0 C to give alkylated products. 2-aryl-1 -silylpropanes.- while allyltrimethylsilane did not give the alkylated product but instead dimerized to give the allylsilylation product.. S-itrimethylsilyli-d-itrimethylsilylrnethyl)- 1-pentene (Eq. (1 )). In the alkylation reaction, the reactivity of allylsilanes increased as the number of chlorine... 

The substituent effect of vinylsilanes is similar to that of allylsilanes. The reactivity of vinylsilanes increased as the number of chlorine atoms on the silicon increased, but decreased as the number of methyl groups increased. However, vinyltrimethylsilane does not react with benzene to give alkylated products. " In the aluminum chloride-catalyzed alkylation of arenes with allylsilanes or vinylsilanes, one or more chlorine substituents on the silicon atom of silanes are required. 

In extension of the alkylation reactions to polychlorobenzenes, polychlorinated benzenes such as 1,2,4-trichlorobenzene and 1,2,., 4-tetrachlorobenzene were alkylated with (l,2-dichloroethyl)trichlorosilanes in the presence of aluminum chloride catalyst. Although the electron-withdrawing chlorine substituents on the ring deactivated the electrophilic substitution reaction, the alkylation... 

Dihalocarbene complexes are useful precursors to new carbenes by nucleophilic displacement of the chlorine substituents. This has been nicely illustrated for Fe(TPP)(=CCl2) by its reaction with two equivalents of Re(CO)5J to give the unusual /t-carbido complex Fe(TPP)=C=Re(CO)4Re(CO)5 which also contains a rhenium-rhenium bond. " The carbido carbon resonance was observed at 211.7 ppm in the C NMR spectrum. An X-ray crystal structure showed a very short Fe=C bond (1.605(13) A, shorter than comparable carbyne complexes) and a relatively long Re=C bond (1.957( 12) A) (Fig. 4, Table III). " ... 

More recently, another class of organic chlorine compounds has emerged as an environmental hazard. These are the dioxins, which, like DDT, contain ring compounds with chlorine substituents. A relatively simple example is 2,3,7,8-tetrachlorodibenzo-p-dioxin ... 

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