Sources of Natural Oil Polyols
Ninety percent of the fatty acids that make up castor oil is ricinoleic acid, which has a hydroxyl group on C-12 and a carbon-carbon double bond. The structure below shows the major component of castor oil which is composed of the tri-ester of rincinoleic acid and glycerin:
Other vegetable oils - such as soy bean oil, peanut oil, and canola oil - contain carbon-carbon double bonds, but no hydroxyl groups. There are several processes used to introduce hydroxyl groups onto the carbon chain of the fatty acids, and most of these involve oxidation of the C-C double bond. Treatment of the vegetal oils with ozone cleaves the double bond, and esters or alcohols can be made, depending on the conditions used to process the ozonolysis product. The example below shows the reaction of triolein with ozone and ethylene glycol.
Air oxidation, (autoxidation), the chemistry involved in the "drying" of drying oils, gives increased molecular weight and introduces hydroxyl groups. The radical reactions involved in autoxidation can produce a complex mixture of crosslinked and oxidized triglycerides. Treatment of vegetable oils with peroxy acids gives epoxides which can be reacted with nucleophiles to give hydroxyl groups. This can be done as a one-step process. Note that in the example shown below only one of the three fatty acid chains is drawn fully, the other part of the molecule is represented by "R1" and the nucleophile is unspecified. Earlier examples also include acid catalyzed ring opening of epoxidized soybean oil to make oleochemical polyols for polyurethane foams and acid catalyzed ring opening of soy fatty acid methyl esters with multifunctional polyols to form new polyols for casting resins.
Triglycerides of unsaturated (containing carbon-carbon double bonds) fatty acids or methyl esters of these acids, can be treated with carbon monoxide and hydrogen in the presence of a metal catalyst to add a -CHO (formyl) groups to the chain (hydroformylation reaction) followed by hydrogenation to give the needed hydroxyl groups. In this case R1 can be the rest of the triglyceride, or a smaller group such as methyl (in which case the substrate would be similar to biodiesel). If R=Me then additional reactions like transesterification are needed to build up a polyol.
Read more about this topic: Natural Oil Polyols
Famous quotes containing the words sources of, sources, natural and/or oil:
“I count him a great man who inhabits a higher sphere of thought, into which other men rise with labor and difficulty; he has but to open his eyes to see things in a true light, and in large relations; whilst they must make painful corrections, and keep a vigilant eye on many sources of error.”
—Ralph Waldo Emerson (1803–1882)
“My profession brought me in contact with various minds. Earnest, serious discussion on the condition of woman enlivened my business room; failures of banks, no dividends from railroads, defalcations of all kinds, public and private, widows and orphans and unmarried women beggared by the dishonesty, or the mismanagement of men, were fruitful sources of conversation; confidence in man as a protector was evidently losing ground, and women were beginning to see that they must protect themselves.”
—Harriot K. Hunt (1805–1875)
“Yet I experienced sometimes that the most sweet and tender, the most innocent and encouraging society may be found in any natural object, even for the poor misanthrope and most melancholy man. There can be no very black melancholy to him who lives in the midst of nature and has his senses still.”
—Henry David Thoreau (1817–1862)
“As a rule they will refuse even to sample a foreign dish, they regard such things as garlic and olive oil with disgust, life is unliveable to them unless they have tea and puddings.”
—George Orwell (1903–1950)