Ethyl alcohol, from molasses

The most important conversions in the context of green chemistry is with the help of enzymes. Enzymes are also referred to as biocatalysts and the transformations are referred to as biocatalytic conversions. Enzymes are now easily available and are an important tool in organic synthesis. The earliest biocatalytic conversion known to mankind is the manufacture of ethyl alcohol from molasses, the mother liquor left after the crystallisation of cane sugar from concentrated cane juice. This transformation is brought about by the enzyme invertase which converts sucrose into glucose and fructose and finally by the enzyme zymase which converts glucose and fiuctose into ethyl alcohol. It is well known that most of the antibiotics have been prepared using enzymes (enzymatic fermentation). 

Method 2B Preparation of 95% ethyl alcohol from table sugar, brown sugar, molasses, or... 

Butanol, which at one time was an unwanted by-product in the preparation of acetone, is now the most important product of the fermentation. The building of a large new factory in Puerto Rico using 10,000 tons of molasses per annum for its production is an indication of this importance. Butanol is probably still the best solvent for cellulose nitrate lacquers. Dibutyl phthalate is certainly the most widely used plasticizer for synthetic resins, and butyl oleate, tributyl citrate and dibutyl tartrate have also been described as plasticizers. Another important use of butanol is as a source of butadiene, which serves as an intermediate in the conversion of sucrose into a synthetic rubber. Although in recent years other methods have been described for the preparation of butanol (for example, from ethyl alcohol and from acetylene), yet the fermentation of carbohydrates is still the cheapest process. 

Molasses. Molasses is the final effluent obtained in the preparation of sugar by repeated crystallization. The sugar it contains cannot be removed economically. The molasses from cane sugar is most commonly known as blackstrap and that from beet is called beet molasses. Molasses is mainly used for the manufacture of ethyl alcohol (ethanol), yeast, and cattle feed. Another use of sweet molasses is in cooking, spreads for bread, topping for pancakes, and in the manufacture of alcoholic beverages. 

In industry ethyl alcohol is widely used as a solvent for lacquers, varnishes, perfumes, and flavorings as a medium for chemical reactions and in recrystallizations. In addition, it is an important raw material for synthesis after we have learned more about the reactions of alcohols (Chap. 16), we can better appreciate the role played by the leading member of the family. For these industrial purposes ethyl alcohol is prepared both by hydration of ethylene and by fermentation of sugar from molasses (or sometimes starch) thus its ultimate source is petroleum, sugar cane, and various grains. 

Propyl hydroxid—Ethyl carbinol—Primary propyl alcohol— CH3,CH2,CH,0H—60—is produced, along with ethylic alcohol,dur-ing fermentation, and obtained by fractional distillation of marc brandy, from cognac oil, huile de marc (not to be confounded with oil of wine), an oily matter, possessing the flavor of inferior brandy, which separates from marc brandy, distilled at high temperatures and from the residues of manufacture of alcohol from beet-root, grain, molasses, etc. It is a colorless liquid, has a hot alcoholic taste, and a fruity odor boils at 96°.7 (306°.l F.) and is miscible with -water. It has not been put to any use in the arts. Its intoxicating and poisonous actions are greater than those of ethyl alcohol. It exists in small quantity in cider. 

Twenty-five years ago the only oxygenated aliphatics produced in important quantities were ethyl and n-butyl alcohols and acetone made by the fermentation of molasses and grain, glycerol made from fats and oils, and methanol and acetic acid made by the pyrolysis of wood. In 1927 the production of acetic acid (from acetylene) and methanol (from synthesis gas) was begun, both made fundamentally from coal. All these oxygenated products are still made from the old raw materials by the same or similar processes, but the amount so made has changed very little in the past quarter century. Nearly all the tremendous growth in the production of this class of compounds has come from petroleum hydrocarbons. 

Rum is made from fermented molasses. It contains from 45 to 55 per cent alcohol. The flavor of rum is largely due to the ethyl butyrate and ethyl formate which it contains. 

---