Alkyl dichlorides

Secondary or tertiary alkyl halides are much less reactive. For example an alkyl dichloride with a primary and a secondary chloride substituent reacts selectively by exchange of the primary chloride. The reactivity with respect to the Finkelstein reaction is thus opposite to the reactivity for the hydrolysis of alkyl chlorides. For the Finkelstein reaction on secondary and tertiary substrates Lewis acids may be used," e.g. ZnCla, FeCls or MesAl. 

Lead di-n-propyl dichloride is more stable than most of the lead di alkyl dichlorides. In contact with water or alcohol at 30° C. it slowly splits ofl lead chloride, and when heated to 228° C. it decomposes. 

The reactivity of di-Grignard reagents can be modified using a variety of metal catalysts. Primary a,co-alkyl di-Grignard reagents, best prepared from alkyl dichlorides in THF, react with silver(I) triflate to form four, five, and six-membered rings in reasonable (40-90%) yields. The reaction is less effective for formation of medium-sized rings, but it is applicable to formation of norbornane 102 from the dichloride 101, as shown in Eq. (41) [80]. 

The most widely used methods of preparation are based on reactions of sodium polysulfides with alkyl dichlorides... 

Polymerization of 1,3-pentadiene can potentially result in five different insertions of the monomers. These are 1,4-cis, 1,4-trans, 1,2-cis, 1,2-trans, and 3,4. In addition, there are potentially 3-cis-l,4 and 3 trans-1,4 stmctures (isotactic, syndiotactic, and atactic). Formations of trans-1,4 isotactic, cis-1,4 isotactic, and cis-1,4 syndiotactic polymers are possible with Ziegler-Natta catalysts [136-138]. Amorphous polymers also form that are predominantly cis-1,4 or trans-1,4, but lack tactic order. Stereospecificity in poly (1,3-pentadiene) is strongly dependent upon the solvent used during the polymerization. Thus, cis-1,4 syndiotactic polymers form in aromatic solvents and trans-1,2 in aliphatic ones. The preparations require cobalt halide/aluminum alkyl dichloride(or dialkyl chloride) catalysts in combinations with Lewis bases. To form a trans-1,4 structure, a catalyst containing aluminum to titanium ratio close to 5 must be used [139]. 

Alkyltin Intermedia.tes, For the most part, organotin stabilizers are produced commercially from the respective alkyl tin chloride intermediates. There are several processes used to manufacture these intermediates. The desired ratio of monoalkyl tin trichloride to dialkyltin dichloride is generally achieved by a redistribution reaction involving a second-step reaction with stannic chloride (tin(IV) chloride). By far, the most easily synthesized alkyltin chloride intermediates are the methyltin chlorides because methyl chloride reacts directiy with tin metal in the presence of a catalyst to form dimethyl tin dichloride cleanly in high yields (21). Coaddition of stannic chloride to the reactor leads directiy to almost any desired mixture of mono- and dimethyl tin chloride intermediates ... 

The other commercially important routes to alkyltin chloride intermediates utilize an indirect method having a tetraalkjitin intermediate. Tetraalkyltins are made by transmetaHation of stannic chloride with a metal alkyl where the metal is typicaHy magnesium or aluminum. Subsequent redistribution reactions with additional stannic chloride yield the desired mixture of monoalkyl tin trichloride and dialkyltin dichloride. Both / -butjitin and / -octjitin intermediates are manufactured by one of these schemes. 

PMMA is not affected by most inorganic solutions, mineral oils, animal oils, low concentrations of alcohols paraffins, olefins, amines, alkyl monohahdes and ahphatic hydrocarbons and higher esters, ie, >10 carbon atoms. However, PMMA is attacked by lower esters, eg, ethyl acetate, isopropyl acetate aromatic hydrocarbons, eg, benzene, toluene, xylene phenols, eg, cresol, carboHc acid aryl hahdes, eg, chlorobenzene, bromobenzene ahphatic acids, eg, butyric acid, acetic acid alkyl polyhaHdes, eg, ethylene dichloride, methylene chloride high concentrations of alcohols, eg, methanol, ethanol 2-propanol and high concentrations of alkahes and oxidizing agents. 

Methylphenol is converted to 6-/ f2 -butyl-2-methylphenol [2219-82-1] by alkylation with isobutylene under aluminum catalysis. A number of phenoHc anti-oxidants used to stabilize mbber and plastics against thermal oxidative degradation are based on this compound. The condensation of 6-/ f2 -butyl-2-methylphenol with formaldehyde yields 4,4 -methylenebis(2-methyl-6-/ f2 butylphenol) [96-65-17, reaction with sulfur dichloride yields 4,4 -thiobis(2-methyl-6-/ f2 butylphenol) [96-66-2] and reaction with methyl acrylate under base catalysis yields the corresponding hydrocinnamate. Transesterification of the hydrocinnamate with triethylene glycol yields triethylene glycol-bis[3-(3-/ f2 -butyl-5-methyl-4-hydroxyphenyl)propionate] [36443-68-2] (39). 2-Methylphenol is also a component of cresyHc acids, blends of phenol, cresols, and xylenols. CresyHc acids are used as solvents in a number of coating appHcations (see Table 3). 

The bulk of 4-methylphenol is used in the production of phenoHc antioxidants. The alkylation of 4-methylphenol with isobutylene under acid catalysis yields 2-/ f2 -butyl-4-methylphenol [2409-55-4] and 2,6-di-/ f2 -butyl-4-methylphenol [128-37-0]. The former condenses with formaldehyde under acid catalysis to yield 2,2 -methylene bis(6-/ f2 -butyl-4-methylphenol) [119-47-1], which is widely used in the stabilization of natural and synthetic mbber (43). The reaction of 2-/ l -butyl-4-methylphenol with sulfur dichloride yields 2,2 -thiobis(6-/ l -butyl-4-methylphenol) [90-66-4]. 

Many organic hahdes, especially alkyl bromides and iodides, react direcdy with tin metal at elevated temperatures (>150° C). Methyl chloride reacts with molten tin metal, giving good yields of dimethyl tin dichloride, which is an important intermediate in the manufacture of dimethyl tin-ha sed PVC stabilizers. The presence of catalytic metallic impurities, eg, copper and zinc, is necessary to achieve optimum yields (108) ... 

The reaction of higher alkyl chlorides with tin metal at 235°C is not practical because of the thermal decomposition which occurs before the products can be removed from the reaction zone. The reaction temperature necessary for the formation of dimethyl tin dichloride can be lowered considerably by the use of certain catalysts. Quaternary ammonium and phosphonium iodides allow the reaction to proceed in good yield at 150—160°C (109). An improvement in the process involves the use of amine—stannic chloride complexes or mixtures of stannic chloride and a quaternary ammonium or phosphonium compound (110). Use of these catalysts is claimed to yield dimethyl tin dichloride containing less than 0.1 wt % trimethyl tin chloride. Catalyzed direct reactions under pressure are used commercially to manufacture dimethyl tin dichloride. 

More useful than the preceding methods is cleavage of alkoxides by acetyl chloride or bromide. One, two, three, or four alkoxyls can be replaced by chloride or bromide. Benzoyl chloride gives poor yields, however. The tri- and tetrachlorides, which are stronger Lewis acids than mono- and dichlorides, coordinate with the alkyl acetate formed and yield distillable complexes (46,55,56). 

This can be circumvented by choosing alkyl groups with no P H, eg, methyl, neopentyl, trimethylsilylmethyl, phenyl and other aryl groups, and benzyl. The linear transition state for -elimination can also be made stericaHy impossible. The most successful technique for stabilization combines both principles. The pentahaptocyclopentadienyl ring anion (Cp) has six TT-electrons available to share with titanium. Biscyclopentadienyltitanium dichloride... 

Using a solution process, the choice of catalyst system is determined, among other things, by the nature of the third monomer and factors such as the width of the mol wt distribution to be realised in the product. A number of articles review the induence of catalyst systems on the stmctural features of the products obtained (3,5—7). The catalyst comprises two main components first, a transition-metal haHde, such as TiCl, VCl, VOCl, etc, of which VOCl is the most widely used second, a metal alkyl component such as (C2H )2A1C1 diethylalurninum chloride, or monoethyl aluminum dichloride, (C2H )AlCl2, or most commonly a mixture of the two, ie, ethyl aluminum sesquichloride, [(C2H )2Al2Cl2]. 

Addition. Addition reactions of ethylene have considerable importance and lead to the production of ethylene dichloride, ethylene dibromide, and ethyl chloride by halogenation—hydrohalogenation ethylbenzene, ethyltoluene, and aluminum alkyls by alkylation a-olefms by oligomerization ethanol by hydration and propionaldehyde by hydroformylation. 

Because of the structural requirements of the bielectrophile, fully aromatized heterocycles are usually not readily available by this procedure. The dithiocarbamate (159) reacted with oxalyl chloride to give the substituted thiazolidine-4,5-dione (160) (see Chapter 4.19), and the same reagent reacted with iV-alkylbenzamidine (161) at 100-140 °C to give the 1 -alkyl-2-phenylimidazole-4,5-dione (162) (see Chapter 4.08). Iminochlorides of oxalic acid also react with iV,iV-disubstituted thioureas in this case the 2-dialkylaminothiazolidine-2,4-dione bis-imides are obtained. Thiobenzamide generally forms linear adducts, but 2-thiazolines will form under suitable conditions (70TL3781). Phenyliminooxalic acid dichloride, prepared from oxalic acid, phosphorus pentachloride and aniline in benzene, likewise yielded thiazolidine derivatives on reaction with thioureas (71KGS471). 

The 1,5-isomers 13.3 (E = S) are colourless, air-stable solids. They are prepared by the cyclocondensation reaction of R2PN2(SiMe3)3 with sulfur dichloride or thionyl chloride. A similar cyclocondensation process, using a mixture of SeCU and Sc2Cl2 as a source of selenium, produces a mixture of the isomers 13.2 and 13.3 (E = Se, R = Ph). The structures of 13.3 (E = S, R = alkyl, aryl) are folded eight-membered rings with a cross-ring S S distance of ca. 2.50 This structural... 

Two approaches for the synthesis of allyl(alkyl)- and allyl(aryl)tin halides are thermolysis of halo(alkyl)tin ethers derived from tertiary homoallylic alcohols, and transmetalation of other allylstannanes. For example, dibutyl(-2-propenyl)tin chloride has been prepared by healing dibutyl(di-2-propenyl)stannane with dibutyltin dichloride42, and by thermolysis of mixtures of 2,3-dimethyl-5-hexen-3-ol or 2-methyl-4-penten-2-ol and tetrabutyl-l,3-dichlorodistannox-ane39. Alternatively dibutyltin dichloride and (dibutyl)(dimethoxy)tin were mixed to provide (dibutyl)(methoxy)tin chloride which was heated with 2,2,3-trimethyl-5-hexen-3-ol40. 

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