Preparation of alkanes

Reduction of Alkyl Halides (RX, X = Cl, Br, or I) (Substitution of Halogen by Hydrogen) 

PRODUCTS WITH MORE CARBONS THAN THE REACTANTS 

Two alkyl groups can be coupled by indirectly reacting two molecules of RX, or RX with R X, to give R—R or R—R. respectively. The preferred method is the Corey-House synthesis, which uses the organometallic lithium dialkylcuprates, RXuLi, as intermediates. 

Problem 4.14 Write equations to show the products obtained from the reactions  

Problem 4.15 Use l-bromo-2-methylbutane and any other one- or two-carbon comfwunds, if needed, to synthesize the following with good yields  

Mixtures of alkanes obtained from petroleum, natural gas and coal can be used as fuel. 

Crude oil is a mixture of alkanes and aromatic hydrocarbons which have carbon atom numbers ranging from 1 to 40. In different regions of the world the composition of oil is different. Crude oil is separated into its components by a method known as fractional distillation. 

Natural gas is a gas mixture which is obtained from underground reservoirs. It consists of methane, a small proportion of ethane and some other gases. 

Alkanes, that are generally extracted from crude oil by fractional distillation, can also be produced in the laboratory. 

Bitumen extracted by the fractional distillation of petroleum is used in asphalt roads. 

The preparation of unfunctionalized alkanes on insoluble supports has only recently received attention. With the aim of preparing ever more elaborate molecules on solid phase, chemists are currently searching for robust methods to assemble complex carbon frameworks on insoluble supports. The synthesis of alkanes has also been investigated in this context. 

Most of the reported preparations of alkanes on insoluble supports can be categorized as either hydrolyses of organometallic compounds, reductions, hydrogenations, or coupling reactions. 

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Preparation of alkanes using lithium di alkylcuprates (Section 14 11) Two alkyl groups may be coupled together to form an alkane by the reaction of an alkyl hal ide with a lithium dialkylcuprate Both alkyl groups must be primary (or meth yl) Aryl and vinyl halides may be used in place of alkyl halides... 

Block, H.-D. and Frohlen, H.-G., Preparation of Alkane Phosphonic and Phos-phinic Acid Aryl Esters, U.S. Patent 4,377,537, 1983. 

Addition of hydrogen atoms to alkenes and alkynes catalytic hydrogenation Preparation of alkanes... 

Preparation of Alkanes by Carbon-Carbon Bond Formation... 

C-Alkylations have been performed with both support-bound carbon nucleophiles and support-bound carbon electrophiles. Benzyl, allyl, and aryl halides or triflates have generally been used as the carbon electrophiles. Suitable carbon nucleophiles are boranes, organozinc and organomagnesium compounds. C-Alkylations have also been accomplished by the addition of radicals to alkenes. Polystyrene can also be alkylated under harsh conditions, e.g. by Friedel-Crafts alkylation [11-16] in the presence of strong acids. This type of reaction is incompatible with most linkers and is generally only suitable for the preparation of functionalized supports. Few examples have been reported of the preparation of alkanes by C-C bond formation on solid phase, and general methodologies for such preparations are still scarce. 

Alkanes are the most highly reduced of all organic compounds. As a consequence, virtually all preparations of alkanes are reductive. Alkenes and alkynes can both be reduced to alkanes by catalytic hydrogenation. While many catalysts can be employed, palladium on carbon is by far die most common. 

A long established method for the preparation of alkanes involves heating an alkyl halide with sodium metal (the Wurtz synthesis). 

Methods for the preparation of alkanes may be divided into a number of groups. Firstly, there are methods that involve the hydrogenolysis of functional groups secondly, there are methods that involve the reduc-... 

There are frequently available aromatic compounds containing aliphatic side chains that are not simple alkyl groups. An alkylbenzene can be prepared from one of these compounds by converting the side chain into an alkyl group. Although there is an aromatic ring in the molecule, this conversion is essentially the preparation of an alkane from some other aliphatic compound. The methods used are those that we have already learned for the preparation of alkanes hydrogenation of a carbon carbon double bond in a side chain, for example. Many problems of the alkylbenzenes are solved by a consideration of simple alkane chemistry. 

Asinger, F., Vogel, H. H. The preparation of alkanes and cycloalkanes, in Houben-Weyl, Methoden der Organischen Chemie (ed. Muller,... 

Chen, J Preparation of Alkane Sulfonic Acids and Sulfonyl Chlorides by Oxidation of Alkanethiols and Dialkyl Disulfides. U.S. Patent 6,124,497,, Sep 26, 2000. 

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