Patent GB-756385-A (GB)
Title: Improvements in the preparation of dialkali derivatives of dimerized aliphatic conjugated olefins and their conversion into unsaturated and saturated dicarboxylic acids
IPC: C07C51/15
Filed: 1954-01-18
Abstract: An aliphatic conjugated diolefin is selectively reacted with finely-divided sodium or potassium in a reaction medium comprising an aliphatic monoether having a methyl group and an oxygen : carbon ratio of not less than 1 : 4 or an aliphatic polyether including those derived from aliphatic polyhydric alcohols having all the OH groups replaced by O-alkyl groups and mixtures thereof in the presence of a minor proportion of a polycyclic aromatic hydrocarbon, at a temperature below 0 DEG  C. to form the corresponding di-alkali metal derivatives of the diolefin dimers. These alkali metal derivatives are of general formula <FORM:0756385/IV(a)/1> where R, R1 and R11 are hydrogen or alkyl radicals, R111 is an alkenyl radical, M is sodium or potassium and m and n are zero or one.  Specified diolefins include butadiene, isoprene, dimethylbutadiene, methyl 1 : 3 pentadiene and other pentadienes.  The finely-divided sodium or potassium may be dispersed in isooctane, di-n-butyl ether, n-octane, n-heptane or straight run kerosene.  If desired, a sodium alloy containing a major proportion of sodium such as sodium-potassium, sodium-calcium or sodium-lithium may be used.  An emulsifier such as the dimer of linoleic acid may be present in the dispersion. Specified aliphatic mono, ether reaction media include dimethyl ether-methyl ethyl ether, methyl n-propyl ether, and methyl isopropyl ether.  Aliphatic polyethers specified include dimethyl, methyl ethyl, diethyl, methyl butyl, ethyl butyl, dibutyl, butyl lauryl and other dialkyl ethylene glycol ethers, trimethylene glycol dimethyl ether, glycerol trimethyl ether, glycerol dimethyl ethyl ether, and diethylene glycol methyl ethyl ether, as well as dioxane, glycol formal, methyl glycerol formal, ethyl and methyl orthoformates, methylal and other acetals.  The polycyclic aromatic hydrocarbon may have condensed rings (napthalene, phenanthrene) or uncondensed rings (diphenyl, terphenyl, dinaphthyl, tetraphenyl ethylene) and may be used in amount from 0.1 to 10 per cent by weight based on the amount of diolefin.  The reaction temperature may be between 0 DEG  and - 50 DEG  C.  Preparation of dicarboxylic acids.-The dialkali-metal diolefin dimers may be carbonated, for example by pouring the reaction mixture on to solid CO2, to form the dialkali-metal salts of the unsaturated dicarboxylic acids containing 2 more carbon atoms in the molecule than the dimer.  These salts may then be hydrolysed to give the unsaturated acids and hydrogenated to give the corresponding saturated acids.  In an example, butadiene is passed into a suspension of finely-divided sodium in isooctane which is mixed with a reaction medium (dimethyl ester) containing p-terphenyl, at - 25 DEG  C.  The disodium derivatives of the butadiene dimers are carbonated by pouring the reaction mixture on to solid CO2. Evaporation of the solvents gives a mixture of the sodium salts of C10 unsaturated dicarboxylic acids. This mixture is hydrogenated using a nickel catalyst and hydrolysed with mineral acid to give a mixture of 2,5-diethyl adipic acid, 2-ethyl suberic acid, sebacic acid and 3-ethyl suberic acid.  In other examples isoprene and methyl pentadienes are used.