CS240718B1 - Alpha-hydroxyisobutyric esters and their preparation - Google Patents

Abstract

Esters of alpha-hydroxyisobutyric acid of the formula CH3 HO—C—OOOR CH3 where R denotes an alkyl with a number of carbon atoms of 8 to 20 and a method of their preparation, which consists in reacting a mixture of acetocyanic anhydride and a monohydric alcohol with a number of carbon atoms of 8 to 20 with hydrochloric acid at a temperature of 40 to 110 °C, the esters formed are separated from the hydrochloric acid, neutralized and the volatile components are distilled off from them. The esters formed are defined compounds with a precise content of hydro groups and as a result are preferably usable in lubricants or as additives in polymers.

Description

Alpha-hydroxyisobutyric acid esters of the formula

CH3

HO — C — OOOR

CH3 where R is an alkyl having from 8 to 20 carbon atoms and a method for preparing said mixture by reacting a mixture of acetone cyanohydride and a monohydric alcohol having from 8 to 20 carbon atoms with hydrochloric acid at a temperature of 40 to 110 ° C; hydrochloric acid, neutralize and distill off the volatiles.

The resulting esters are defined compounds with a precise hydro group content and, as a result, are useful preferably in lubricants or as additives for polymer polymers.

The present invention relates to novel alpha-hydroxyisobutyric acid esters and processes for their preparation.

The esters known to date have been prepared by esterifying alpha-hydroxyisomeric acid with alcohols containing 1 to 5 carbon atoms. Esters of C 1 -C 2 alcohols were also prepared by saturating the alcohols with dry hydrogen chloride, followed by treatment with acetone cyanohydrin and finally with water. The hitherto known esters of higher molecular weight alcohols with carboxylic acids, which contain, besides ester linkages, also free hydroxy groups, are prepared from isolated polyfunctional alcohols and carboxylic acids. These processes always produce a mixture of esters with a low content of hydroxyl groups, which is disadvantageous in their further use, for example as base materials for ester lubricating oils. The novel esters prepared according to the invention provide defined compounds with a precise hydroxyl content, allowing their subsequent use as additives to polymers, lubricant components and the like.

Novel esters of formula (I)

CHs

HO — C — COOR. ' CHs (I), wherein R is an alkyl of 8 to 20, are prepared according to the invention by reacting a mixture of acetone cyanohydrin and a monovalent alcohol or a mixture of monohydric alcohols having a carbon number of 8 to 20 with an acid hydrochloric acid at 40 DEG-110 DEG C., the esters formed are separated from the hydrochloric acid, neutralized and the volatiles are separated. Upon addition of hydrochloric acid, an exothermic reaction occurs, a rapid rise in the reaction temperature, which stops at 110 ° C. The reaction is likely to occur via iminoether hydrochloride followed by saponification. It is preferred to heat the mixture of acetone cyanohydrin and alcohol to 80-100 ° C and only allow the hydrochloric acid to the bottom of the reaction vessel while stirring. Under these conditions the reaction proceeds continuously at 110 ° C and the rate of addition of hydrochloric acid is controlled by reflux. If a short column with a layer of Raschig rings is placed in front of the reflux condenser and is moistened with dilute hydrochloric acid at the start of the reaction, the leakage of hydrogen chloride or unreacted acetone cyanohydrin is prevented. The esters obtained are clear, water-soluble liquids of mild ethereal odor having a reactive hydroxy group.

The examples below illustrate embodiments of the invention. ,

He did

In a 4-neck 6-neck Keller flask equipped with a stirrer, azeotropic adapter, thermometer, flask to the bottom of the flask, and an arterial bath, 850 g of acetone cyanohydrin (10 mol) and 1690 g of 2-ethylhexanol (13 mol) were charged. ^C 'C, heating is switched off and stirring is accepted 1400 g of hydrochloric acid 34 ° / o. the reaction temperature rose to 108 ° C during the reaction dropped to 104 ° C, the rate of admission of acid was gradually increased and controlled by reflux with dilute hydrochloric acid The reaction mixture was then heated with stirring at boiling point for 2 h and the remaining 1% hydrochloric acid (835 g) was distilled off over 2 h. At the end of the distillation, the temperature in the flask rose to 130 C. The flask contents were cooled to 60 ° C. and adding 1 water, the ammonium chloride was dissolved and the aqueous solution was then discarded. The mixture was filtered through a pad of anhydrous soda to remove a small amount of dissolved water in the ester. The filtrate (2,435 g) was rectified in a vacuum column (1350 Pa). 380 g of a fraction having a boiling point of 73-85 ° C, unreacted 2-ethylhexano.1, 180 g of an intermediate fraction having a boiling point of 85-106 ° C was obtained. 8.4% of the batch and 1725 g of the desired ester, bp 106-107 ° C, (80% yield).

The ester obtained had the following physicochemical characteristics:

flash point 98 ° C pour point below -70 ° C. ..

an acid number of 0.02 mg KOH / g Density at 20 ° C 0.9211 n _D ²⁰ - 1.4322 (from atomic refraction was calculated as 1.4325) _N; ²⁵ = 1.4303 viscosity in mm ² . s ^_1 at

100 ° C = 1.04 ° C = 2.71 —20 ° G = 71 —40 ° C = 545

The structure and purity were confirmed by NMR analysis. The NMR spectrum was measured in deuterlochloroform with tetramethylsilane as internal standard δ (CH 2 CO 3 = 1.41 δ (OOH 2) = 4.08 ((CH 2 GHz) = 0.89 δ (CH 2) _n = 1.27. / 1, water solubility in ester of less than 10 g / l, lubricity on a four-ball machine (Wear - - Tester - at 175 ° C, 1200 rpm, 392 N), measured by abrasion was 1.65 mm.

EXAMPLE 1 d 2 As in Example 1 was put 850 g of acetone cyanohydrin and ¹ 1690 grams of 2-ethylhexanol and accepted 1,380 g HCl 30%. The hydrochloric acid was distilled off without using the azeotropic capsule during 1% h, a small amount of entrained alcohol was collected and returned to the ester. After dissolution of NH 4 Cl, ester washing, 555 g of alcohol, 260 g of intermediate (12%) and 1640 g of ester (76%) were obtained by rectification: n _D ²⁵ = 1.4303, acid number 0.03 and viscosity at 50 ° C 2, 71 mm ² s ^_1 .

Example 3

In analogy to Example 1, 425 g of acetone cyanohydrin and 845 g of 2-ethylhexanol were introduced, 690 g of 34% hydrochloric acid being allowed. After the addition of the acid, the acid was not distilled off, but after cooling to 70 ° C, 4 L of water were added, the lower layer of NH 4 Cl solution was drained and the remaining ester was washed to neutral. Rectification gave 290 g of alcohol, 140 g of intermediate (13%) and 690 g of ester (58%). The boiling point of the ester = 107 ° C at 1400 Pa, n _D 25 = 1.4303.

Example 4

As in Example 1, 42 (5 g of acetone cyanohydrin and 720 g of 2-ethylhexanol) were added and 1,200 g of hydrochloric acid were allowed, only 17%. After the addition of the acid, the reaction mixture was heated and after stirring stopped containing NHi-Cl forgive ester are washed and rectification. were obtained 500 g of ester boiling at 106 ° C under a pressure of 1350 Pa, n _D ²⁵ = 1.4302.

Example 5

On the apparatus of Example 1, 425 g of acetone cyanohydrin (5.0 mol) and 1 072 g of a mixture containing 85% decanol and 15% dodecanol (6.5 mol) were introduced, the mixture was heated to 100 ° C, the heating was switched off and allowed 700 g of 34% hydrochloric acid for 30 minutes The flask contents were then heated at boiling point for V2 and 415 g of hydrochloric acid were distilled off over 1.5 h.

At 90 ° C, 780 g of water was added to the flask with stirring, 1040 g of ammonium chloride solution were drained, the ester was washed with 0.5 L of 20% soda solution, followed by 0.5 L of water, and filtered through anhydrous soda. 1,410 g of the filtrate were obtained, from which 300 g of the fractions were distilled off at a pressure of 2.6 kPa, boiling 135-145 ° C, the product 1015 g at boiling point 145-175 ° C, acid number 0 02 milligrams of KOH / g, flash point 117 ° C, viscosity at 100 ° C = 1.61 mm ² .s ^-1 , at 50 ° C = 4.32 mm ² .si, at -20 ° C = 111 millimeters ² . s ^-1 , pour point —36 ° C. Example 6

As in Example 5, 560 g of acetone cyanohydrin (6.5 mol), 1670 g of a mixture containing 50% hexadecanol, 30% octadecanol and 20% eicosanol (6.5 mol), 9110 g of hydrochloric acid 34% were treated to dissolve the salts. 900 ml of water at 90 ° C were allowed to wash 800 ml of a 5% soda solution at 90 ° C and 900 ml of water at 90 ° C.

After filtration through anhydrous soda, 255 g of the front portions (11.5%) with a boiling point of 190-225 ° C were distilled from the filtrate at a pressure of 2.6 kPa. The product 1700 g (78.5%) had a boiling point of 226-260 degrees C at this pressure, an acid number of 0.02, a flash point of 192 ° C, a pour point of 27 ° C, a viscosity of 100 ° C = 3.09 mm ^2. . s = ¹ , at 50 ° C = 9.45 mm ² . s ¹ .

Claims (2)

SUBJECT CLAIMS 1. Alpha-hydroxyisobutyric acid esters of the general formula I OHs l · HO — O — OOOR AND CH3 (I) Wherein R represents an alkyl having a carbon number of 8 to 20. 2. A process for the preparation of esters of the formula I according to claim 1, characterized in that the mixture of acetone cyanohydrin and monohydric alcohol or a mixture of monohydric alcohols having a carbon number of 8 to 20 is reacted with hydrochloric acid at 40 to 1 (10 ° C). C. The esters formed are separated from the hydrochloric acid, neutralized and the volatiles are distilled off.