OTHER GLYCOLS

Glycols such as neopentyl glycol, 2,2,4-trimethyl-l,3-pentaiiediol, 1,4-cyclohexanedimethanol, and hydroxypivalyl hydroxypivalate are used in the synthesis of polyesters (qv) and urethane foams (see Foamed plastics). Their physical properties are shown in Table 1 (1 6). 

Properties Neopentyl glycol (1) 2,2,4-Trimethyl-l,3-pent anediol (7) 1,4-Cyclohexane-dimetha nof (8) Hydroxypivalyl hydroxypivalate (9) 

Neopentyl glycol, or 2,2-dimethyl-1,3-propanediol [126-30-7] (1) is a white crystalline soHd at room temperature, soluble ia water, alcohols, ethers, ketones, and toluene but relatively iasoluble ia alkanes (1). Two primary hydroxyl groups are provided by the 1,3-diol stmcture, making this glycol highly reactive as a chemical intermediate. The gem-A methy configuration is responsible for the exceptional hydrolytic, thermal, and uv stabiUty of neopentyl glycol derivatives. 

Chemical Properties. Neopentyl glycol can undergo typical glycol reactions such as esterification (qv), etherification, condensation, and oxidation. When basic kinetic studies of the esterification rate were carried out for neopentyl glycol, the absolute esterification rate of neopentyl glycol with / -butyric acid was approximately 20 times that of ethylene glycol with / -butyric acid (7). 

Manufacture. Commercial preparation of neopentyl glycol can be via an alkah-cataly2ed condensation of isobutyraldehyde with 2 moles of formaldehyde (crossed Canni22aro reaction) (2,8). Yields are - 70%. 

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Other Glycol Nitrates. Other Hquid nitrates have been used as explosive plasticizers for nitroceUulose (Table 8). These may be made by mixed-acid nitration using procedures similar to those used for nitroglycerin. 

An early source of glycols was from hydrogenation of sugars obtained from formaldehyde condensation (18,19). Selectivities to ethylene glycol were low with a number of other glycols and polyols produced. Biomass continues to be evaluated as a feedstock for glycol production (20). 

Trimethylpentanediol is soluble in most alcohols, other glycols, aromatic hydrocarbons, and ketones, but it has only negligible solubiUty in water and ahphatic hydrocarbons (4). 

Chemical Properties. Trimethylpentanediol, with a primary and a secondary hydroxyl group, enters into reactions characteristic of other glycols. It reacts readily with various carboxyUc acids and diacids to form esters, diesters, and polyesters (40). Some organometaUic catalysts have proven satisfactory for these reactions, the most versatile being dibutyltin oxide. Several weak bases such as triethanolamine, potassium acetate, lithium acetate, and borax are effective as stabilizers for the glycol during synthesis (41). 

Decamethylene glycol has been prepared by the reduction of dimethyl sebacate and diethyl sebacate with sodium and ethyl alcohol by the reduction of sebacamide with sodium and amyl alcohol and by the reduction of dimethyl sebacate with sodium and liquid ammonia in absolute alcohol. The reduction of esters with sodium and alcohol has also been applied to the preparation of many other glycols. ... 

The only other glycol that is fairly common is propylene glycol which has a molecular formula of C3H (OH)2. It is a combustible liquid with a flash point of 210°F, and its major use is in organic synthesis, particularly of polyester resins and cellophane. 

A -3-Ketones react easily with ethylene glycol or other glycols in the presence of p-toluenesulfonic acid to give 3-ketals with migration of the 4,5-double bond to the 5,6-position. With 19-nor-A" -3-ketones a mixture of A -and... 

The Dow process consists of the formation of an acid-terminated soft segment, first by the esterification of polyoxyalkylene or other glycol, followed by the reaction of a diisocyanate and additional diacid to form PESA. 

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