DL-Menthol

MENTHOL

3-p-Menthol;4-Isopropyl-1-methylcyclohexan-3-ol;5-methyl-2-(1-methylethyl)-,(1.alpha.,2.beta.,5.alpha.)-(+-)-Cyclohexanol;5-methyl-2-(1-methylethyl)-,(1alpha,2beta,5alpha)-(+/-)-cyclohexano;cis-1,3-trans-1,4-(+-)-mentho;Cyclohexanol, 5-methyl-2-(1-methylethyl)-, (1alpha,2beta,5alpha)-(±;cyclohexanol,5-methyl-2-(1-methylethyl)-,(1-alpha,2-beta,5-alpha);d,1-menthol

15356-70-4

C10H20O

NOOLISFMXDJSKH-UHFFFAOYSA-N

156.27

156.27

239-388-3

White

29061100

Bulk Drug Intermediates

20.2

Physical Properties.The eight optically active menthols differ in their sensory properties. ()-Menthol has a characteristic peppermint odor and also exerts a cooling effect. The other isomers do not possess this cooling effect and are, therefore, not considered to be “refreshing.” Racemic menthol occupies an intermediate position; the cooling effect of the ()-menthol present is distinctly perceptible.The enantiomeric menthols have identical physical properties (apart from their specific rotations), but the racemates differ from the optically active forms in, for example, theirmelting points.Although the differences between the boiling points are small, the (racemic) stereoisomers can be separated by fractional distillation. Boiling points (in °C at 101.3 kPa) are as follows:rac-neomenthol, 211.7rac-neoisomenthol 214.6rac-menthol, 216.5rac-isomenthol, 218.6Other physical constants of commercially available levorotatory and racemic menthols are as follows: ()-menthol, mp 43 °C, [α]20 D 50° (ethanol, 10%); racemic menthol, mp 38 °C.Chemical Properties.Hydrogenation of menthols yields p-menthane; oxidation with chromic acid or catalytic dehydrogenation yields menthones. Dehydration under mild conditions yields 3-p-menthene as the main product. Reaction with carboxylic acids or their derivatives yields menthyl esters, which are used mainly as aroma substances and in pharmaceutical preparations and formulations. The esterification of menthols with benzoic acid is used on an industrial scale in the resolution of racemic menthol.

3.2

0.89 g/mL at 25 °C(lit.)

34-36 °C(lit.)

216 °C(lit.)

200 °F

1.4615

0.42 mg/mL at 25 °C

2-8°C

0.8 mm Hg ( 20 °C)

5.4 (NTP, 1992) (Relative to Air)

The acute oral LD50in rats has been reported as 3180 mg/kg by Jenner, Hagan, Taylor, Cook & Fitzhugh (1964) and as 2900 mg/kg by Herken (1961). The acute oral LD50in cats was reported to be 1500-1600 mg/kg (Flury & Seel, 1926). The sc LD50in the mouse was reported as 1400-1600 mg/kg (Flury & Seel, 1926) and the ip LD50as 750 mg/kg in the rat (Herken, 1961) and 1500-1600 mg/kg in the cat (Flury & Seel, 1926). In rabbits, the ip LD50was reported to be approximately 2000 mg/kg (Herken, 1961), while the acute dermal LD50exceeded 5000 mg/kg (Levenstein, 1973).

2-8°C