Substitution of chlorines

Synthesis of allenic alcohols hy 1., 2-substitution of chlorine on ether groups by hydride... 

Substitution of chlorine dioxide for chlorine in the first (chlorination) bleaching stage (C ) is a strategy that has been widely adopted in North... 

When chlorine dioxide is used for pulp bleaching in conjunction with the Kraft (sulfide) process for chemical pulping, by-product sodium sulfate can be used as a source of makeup sulfur and sodium consumed in the chemical cycle. The demand for sodium and sulfur in pulp bleaching is related to the loss of these chemicals through carryover in unbleached pulp. As process improvements have sought to reduce pollution from pulp mills, less sodium sulfate makeup is required. The trends in pulp bleaching to increase substitution of chlorine with chlorine dioxide have caused an oversupply of sodium sulfate, so that this by-product is often regarded as waste (81). 

The structure of ( )-169 is determined to have a ( )-3a,3a -bispyrrolo[2,3-(j] indole skeleton by carrying out X-ray single crystallographic analysis of its derivative 252 (99H1237). Compound 252 is obtained from ( )-169 by the following sequence of reactions (1) alkaline hydrolysis of ( )-169 to 249 (88%), (2) conversion of 249 to 251 (71%) by treatment with NaH and chloroacetyl chloride, (3) substitution of chlorine on the chloroacetyl group for acetate 252 (93%) by the reaction with NaOAc. 

Substitution of chlorine in 3-chloro-l,2,4-benzotiiazine 1-oxide 49 by treatment with NaCN in methanol affords 3-methoxy-l,2,4-benzotriazine 1-oxide 52 (77GEP2538179). 

It may not be appropriate to compare the thermal stability characteristics of VC/VAc copolymer to that of a VC homopolymer (PVC). The copolymerization would involve different kinetics and mechanism as compared to homopolymerization resulting structurally in quite different polymers. Hence, copolymerization of VC with VAc cannot be regarded as a substitution of chlorines in PVC by acetate groups. To eliminate the possibility of these differences Naqvi [45] substituted chlorines in PVC by acetate groups, using crown ethers (18-crown-6) to solubilize potassium acetate in organic solvents, and studied the thermal stability of the modified PVC. Following is the mechanism of the substitution reaction ... 

Naqvi and Joseph [139] studied the kinetics of acet-oxylation of PVC using 18-crown-6 to solubilize KOAc in organic solvents under mild reaction conditions. They concluded that the substitution of chlorines in PVC by acetoxy groups proceeded by an Sn mechanism. 

Table 2. Yield of nucleophilic substitution of chlorine in [FeCp(C6H5Cl)]+ by amino groups using amines at 20 °C...

A phenylsulphinyl group has been found to promote the nucleophilic substitutions of chlorine at positions ortho and para to the aromatic ring (equation 313)609. 

Some PCB congeners have coplanar structures (see, e.g., 3,4,3, 4 -tetrachloro-biphenyl in Figure 6.1). The coplanar conformation is taken up when there is no chlorine substitution in ortho positions. If there is substitution of chlorine in only one ortho position, the molecule may still be close to coplanarity, because of only limited interaction between Cl and H on adjoining rings. Substitution of chlorines in... 

The pulp and paper industry is the largest industrial process water user in the U.S.5 In 2000, a typical pulp and paper mill used between 15,140 and 45,420 L (4000 to 12,000 gal) of water per ton of pulp produced. 1 2 3 4 General water pollution concerns for pulp and paper mills are effluent solids, biochemical oxygen demand (BOD), and color. Toxicity concerns historically occurred from the potential presence of chlorinated organic compounds such as dioxins, furans, and others (collectively referred to as adsorbable organic halides, or AOX) in wastewaters after the chlorination/ extraction sequence. With the substitution of chlorine dioxide for chlorine, discharges of the chlorinated compounds have decreased dramatically. 

It is not unreasonable that the substitution of chlorines onto the acenaphthylene ring should have such a significant influence on the intersystem crossing processes, kd and lsc. It is somewhat surprising, however, that the other processes involving spin-inversion were affected to such a small extent. 

Different substituents on the carboxy-functionalized fluorescein can be introduced to produce marked alterations in the absorbance and fluorescence emission wavelengths, as well as in other physical properties. The selective substitution of chlorine for aromatic hydrogen has been found to increase fluorescence efficiency and to narrow emission and absorbance maxima when compared with fluorescein 48, which is useful in multicolor imaging. 

Substitution of two chlorines in (l,2-benzenedioxy)trichlorophosphorane by N,0 bis(trimethylsilyl)amino acids gives 34 (X = Cl) further substitution of chlorine by phenol gives 34 (X = OPh) (Scheme 22) <1998S855>. The reaction of P(NMe2)3 with 2-aminophenols generates aminophosphoranes 33 (R = H, Buc) (Equation 20) <2000HAC11>. 

The interesting complex chemistry of rhodium has been rather neglected this is probably because most of the synthetic methods for obtaining complexes have been tedious. In general, substitutions of chlorine atoms bonded to rhodium by other ligands are slow, and products have usually been mixtures. The situation is now changing, since novel catalytic approaches to rhodium complexes have been developed.1 The catalysis in the present synthesis involves the rapid further reaction of the hydrido complex formed from l,2,6-trichIorotri(pyridine)rho-dium(III) in the presence of hypophosphite ion. 

An abnormal (tele) substitution of chlorine in both 2,3- and 2,6-dichloropyrazines 91, 92 occurred on reaction with dithiane anion, while morpholine gave the normal //wo-substitution <06TL31>. Another paper described the highly selective ipso monosubstitution of the 2,3-dichloro compound by enolates in toluene <06T9919>. 

In many cases, the yields of these products are high. However, the use of /V-silylated triazoles as nucleophiles or the use of cyclic nitroso acetals (475) substituted at the C-3 atom leads to a noticeable decrease in the yield of the oximes. Therefore, steric hindrance in nitroso acetals and a decrease in nucleophilicity of A-centered nucleophiles result in an increase in the contribution of side reactions. It should be emphasized that C -nucleophiles, such as anions of nitro compounds, are not involved in coupling reactions with cyclic nitroso acetals (475). However, the products, which formally correspond to the C,C-coupling mechanism, can be prepared by the nucleophilic substitution of chlorine in compound (476 d) by a Sa/2 mechanism (Scheme 3.254, product (483c), the yield was 79%). 

Sulfur atom as internal nucleophile. In this area, it has been shown that the reaction of 8-bromo-l,3-dimethyl-7-(2,3-epithiopropyl)xanthine 147 with a range of aliphatic and aromatic amines generates efficiently 2-amino-substituted 2,3-dihydro-thiazolo[2,3-/]xanthine derivatives 148. The process involves a sequential amine-induced thiirane ring opening followed by thiolate z/MYi-substitution of chlorine atom (Equation 66) <1994PCJ647>. 

Chlordane is subject to hydrolysis via the nucleophilic substitution of chlorine by hydroxyl ions to yield 2,4,5,6,7,8,8-heptachloro-3a,4,7,7a-tetrahydro-4,7-methano-l//-indene which is resistant to hydrolysis (Kollig, 1993). The hydrolysis half-life at pH 7 and 25 °C was estimated to be >197,000 yr (Ellington et ah, 1988). 

Nucleophilic substitution of chlorine in 2,4-dinitrochlorobenzene by diethylamino group from triethylamine (Scheme 4.18) is a rare example when both the formed opposite-charged ion radicals exist together in the bulk solution for a long time. 

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