Butanes chlorination

From these and similar reactions, it s possible to calculate a reactivity order toward chlorination for different sorts of hydrogen atoms in a molecule. Take the butane chlorination, for instance. Butane has six equivalent primary hydrogens (-CH3) and four equivalent secondary hydrogens (-CH2-). The fact that butane yields 30% of 1-chlorobutane product means that each one of the six primary hydrogens is responsible for 30% -e 6 = 5% of the product. Similarly, the fact that 70% of 2-chlorobutane is formed means that each of the four secondary hydrogens is responsible for 70% -e 4 = 17.5% of the product. Thus, reaction of a secondary hydrogen happens 17.5% + 5% = 3.5 times as often as reaction of a primary hydrogen. 

Methane ethane and cyclobutane share the common feature that each one can give only a single monochloro derivative All the hydrogens of cyclobutane for example are equivalent and substitution of any one gives the same product as substitution of any other Chlorination of alkanes m which the hydrogens are not all equivalent is more com plicated m that a mixture of every possible monochloro derivative is formed as the chlo rmation of butane illustrates... 

These two products arise because m one of the propagation steps a chlorine atom may abstract a hydrogen atom from either a methyl or a methylene group of butane... 

A single secondary hydrogen m butane is abstracted by a chlorine atom 3 9 times faster than a single primary hydrogen... 

Addition to double bonds is not the only kind of reaction that converts an achiral molecule to a chiral one Other possibilities include substitution reactions such as the formation of 2 chlorobutane by free radical chlorination of butane Here again the prod uct IS chiral but racemic... 

Chlorination or bromination of methane, ethylene, etc Maleic anhydride (from butane)... 

In the presence of catalysts, trichloroethylene is readily chlorinated to pentachloro- and hexachloroethane. Bromination yields l,2-dibromo-l,l,2-trichloroethane [13749-38-7]. The analogous iodine derivative has not been reported. Fluorination with hydrogen fluoride in the presence of antimony trifluoride produces 2-chloro-l,l,l-trifluoroethane [75-88-7] (8). Elemental fluorine gives a mixture of chlorofluoro derivatives of ethane, ethylene, and butane. 

Another experiment of the competition type involves the comparison of the reactivity of different atoms in the same molecule. For example, gas-phase chlorination of butane can lead to 1- or 2-chlorobutane. The relative reactivity k /k of the primary and secondaiy hydrogens is the sort of information that helps to characterize the details of the reaction process. 

The value of k /k can be determined by measuring the ratio of the products 1-chlorobutane 2-chlorobutane during the course of the reaction. A statistical correction must be made to take account of the fact that the primary hydrogens outnumber the secondaiy ones by 3 2. This calculation provides the relative reactivity of chlorine atoms toward the primary and secondary hydrogens in butane ... 

If every collision of a chlorine atom with a butane molecule resulted in hydrogen abstraction, the n-butyl/5ec-butyl radical ratio and, therefore, the 1-chloro/2-chlorobutane ratio, would be given by the relative numbers of hydrogens in the two equivalent methyl groups of CH3CH2CH2CH3 (six) compared with those in the two equivalent methylene groups (four). The product distribution expected on a statistical basis would be 60% 1-chloro-butane and 40% 2-chlorobutane. The experimentally observed product distribution, however, is 28% 1-chlorobutane and 72% 2-chlorobutane. 5ec-Butyl radical is therefore formed in greater anounts, and n-butyl radical in lesser anounts, than expected statistically. 

The situation is even worse for chlorination of alkanes that have more than one sort of hydrogen. For example, chlorination of butane gives two mono-chlorinated products in addition to dichlorobutane, trichlorobutane, and so on. Thirty percent of the monochloro product is 1-chlorobutane, and seventy percent is 2-chlorobutane. 

Chlorine Ammonia, acetylene, butadiene, butane or other petroleum gases, hydrogen, sodium carbide, turpentine, benzene or finely divided metals... 

Hydrocarbons (benzene, butane, Fluorine, chlorine, bromine, chromic acid, peroxide... 

With the growing prominence of the petrochemicals industry this technology was, in turn, replaced by direct air oxidation of naphtha or butane. Both these processes have low selectivities but the naphtha route is still used since it is a valuable source of the co-products, formic and propanoic acid. The Wacker process, which uses ethylene as a feedstock for palladium/copper chloride catalysed synthesis of acetaldehyde, for which it is still widely used (Box 9.1), competed with the direct oxidation routes for a number of years. This process, however, produced undesirable amounts of chlorinated and oxychlorinated by-products, which required separation and disposal. 

Solvent-assisted decaffeination of coffee can result in residues of solvent reaching the consumer.208 The use of chlorinated hydrocarbon solvents such as chloroform,209 methylene chloride, trichloroethylene,208 and difluoromonochloromethane (Freon),210 will probably be replaced by compounds already found in roasted coffee. The use of an ethyl acetate and 2-butanone mixture leaves a 26-ppm residue in green coffee, but zero residue in roasted coffee.211 Other solvent compounds used or suggested for coffee improvement or decaffeination include propane, butane,212 carbon dioxide,213 214 acetone215 dimethyl succinate,2161,1-dimethoxymethane, and 1,1-dimethoxyethane.217 Of all these, supercritical carbon dioxide, ethyl acetate, and methylene chloride are the solvents most used currently in decaffeination processes. 

On the other hand, there is no evidence to support the assertion that polyethylene vapor berries deteriorate with exposure to soil chemicals. Construction film is a low-density polyethylene. High-density polyethylenes are used for the storage and transportation of an array of chemicals. Polyethylene is chemically stable, but may be adversely affected by aliphatic hydrocarbons (such as hexane, octane, and butane) and chlorinated solvents. It does not appear to be reactive with the acids and salts likely to be encountered in soil and concrete. 

Table 7.2 Kinetic parameters and physical data for the chlorination of butanic acid.

Chlorine dioxide Copper Fluorine Hydrazine Hydrocarbons (benzene, butane, propane, gasoline, turpentine, etc) Hydrocyanic acid Hydrofluoric acid, anhydrous (hydrogen fluoride) Hydrogen peroxide Ammonia, methane, phosphine or hydrogen sulphide Acetylene, hydrogen peroxide Isolate from everything Hydrogen peroxide, nitric acid, or any other oxidant Fluorine, chlorine, bromine, chromic acid, peroxide Nitric acid, alkalis Ammonia, aqueous or anhydrous Copper, chromium, iron, most metals or their salts, any flammable liquid, combustible materials, aniline, nitromethane... 

Give the equation for the reaction between butane and one mole of chlorine gas. What are the conditions for the reaction (2)... 

Photolytic. Major products reported from the photooxidation of butane with nitrogen oxides under atmospheric conditions were acetaldehyde, formaldehyde, and 2-butanone. Minor products included peroxyacyl nitrates and methyl, ethyl and propyl nitrates, carbon monoxide, and carbon dioxide. Biacetyl, tert-butyl nitrate, ethanol, and acetone were reported as trace products (Altshuller, 1983 Bufalini et al, 1971). The amount of sec-butyl nitrate formed was about twice that of n-butyl nitrate. 2-Butanone was the major photooxidation product with a yield of 37% (Evmorfopoulos and Glavas, 1998). Irradiation of butane in the presence of chlorine yielded carbon monoxide, carbon dioxide, hydroperoxides, peroxyacid, and other carbonyl compounds (Hanst and Gay, 1983). Nitrous acid vapor and butane in a smog chamber were irradiated with UV light. Major oxidation products identified included 2-butanone, acetaldehyde, and butanal. Minor products included peroxyacetyl nitrate, methyl nitrate, and unidentified compounds (Cox et al., 1981). 

This would have results in 77 hits from l,2-[propadiene, 1,1,2,2-tetrafluoro-] with a boiling point of —38 °C, to [propane, l,l,l,2,3,3,3-heptafluoro-2-(trifluoromethyl)-] with a boiling point of 0 °C. Out of 77 hits, 49 of them contain elements that include B, Si, N, P, As, O, S, Cl, Br, and I, and perhaps too toxic to be considered as refrigerants seriously. There are 11 hits that are hydrocarbons, such as butane, which would be too flammable to be considered. Perhaps we would eliminate the six hits that have double or triple bonds, as they tend to be less stable and could polymerize. The remaining ones are all hydrofluorocarbons (HECs) without chlorine, and the prime candidates are C2H2E4, C3H3E5, and C4F10. 

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