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Synthesis method for d, l-menthol and stereoisomers thereof

A technology of stereoisomers and synthesis methods, applied in the field of d, can solve the problems of non-reusable hydrocarbon by-products, high equipment requirements, and harsh operating conditions, and achieve mild operating conditions, low equipment requirements, and low reaction temperature Effect

Inactive Publication Date: 2013-04-24
江苏宏邦化工科技有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0012] The conditions for catalytic hydrogenation or isomerization of compounds with menthane carbon skeletons described so far are either reacted in organic solvents, or carried out at high temperature and under excessive pressure, so the equipment requirements are high, the operating conditions are harsh, and it is easy to Causes hydrogenolysis of hydroxyl groups in menthol to generate hydrocarbon by-products that cannot be reused; or requires the use of expensive noble metals as catalysts

Method used

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  • Synthesis method for d, l-menthol and stereoisomers thereof

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Experimental program
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Effect test

Embodiment 1

[0027] Embodiment 1: the preparation of composite Raney nickel catalyst: 625g mass concentration 20% sodium hydroxide aqueous solution, under stirring and ice-water bath cooling, add the aluminum-nickel alloy of 60-100 purpose to contain iron, molybdenum, chromium in batches in fume hood Powder 100g, control the temperature below 25°C and continue stirring for 30 minutes; stop stirring and let the reaction solution rise to room temperature; Overflow; add distilled water continuously during the heating process, so that the volume of the reaction solution is basically constant until the generation of hydrogen slows down again;

[0028] Stand still, until the nickel powder sinks, pour out the supernatant; wash with equal volumes of distilled water and 5% sodium hydroxide aqueous solution with a mass concentration, and pour out the supernatant; repeat the washing with water several times until the aqueous solution is neutral; wherein, In addition to nickel, the catalyst also conta...

Embodiment 2

[0029] Example 2: 3L autoclave, 1500g thymol, 42.9g of the catalyst of Example 1, operate according to the usual hydrogenation procedure: hydrogen pressure 0.1MPa, heated to a temperature of 200°C and stirred for 8 hours, cooled the material, and suction filtered , the product composition obtained is as follows (GC): d, l-neomenthol 27.82%; d, l-neomenthol 1.63%; d, l-menthol 57.77%; d, l-isomenthol 12.18%; d, l-menthone 0.16%; hydrocarbons 0.03%; by fractional distillation under reduced pressure, d, l-menthol, d, l-isomenthol, d, l-neomenthol were obtained respectively; the product yield is the theoretical yield 99.5% of.

Embodiment 3

[0030] Embodiment 3: operate with embodiment 2; Wherein, hydrogen pressure 0.5MPa, temperature 180 ℃ under stirring reaction 10 hours; Wherein, starting material is composed of: thymol 70%, d, l-neomenthol 20.82%, d, l-neeomenthol 5.63%, d, l-menthol 2.77%, d, l-menthone 0.6%, hydrocarbon 0.18%; the composition of the product obtained after the reaction is as follows: d, l-neeomenthol 26.20% , d, l-neo-menthol 1.83%, d, l-menthol 58.79%, d, l-isomenthol 12.5%, d, l-menthone 0.26%, hydrocarbon 0.22%; menthol mixed product The yield is 99.3% of the theoretical yield.

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Abstract

The invention discloses a synthesis method for d, l-menthol and stereoisomers thereof. The synthesis method comprises: a compound Raney nickel is used as a catalyst for the catalytic hydrogenation of compounds containing at least one double bond, connecting to an oxygen atom at 3 - position, and having a menthane carbon skeleton, such as thymol, and d, l-menthol and / or a mixture of stereoisomers thereof; and after the reaction is completed, d, l-menthol, d, l-neomenthol and the d, l-iso-menthol are separately obtained via vacuum distillation in a packed tower with a number of theoretical plates of 60-100; wherein the reaction is carried out under conditions of a pressure being 0.1-3.5MPa and a temperature being 50-200 DEG C. In the whole reaction process of the present invention, water or an organic solvent are not used, the catalyst can be reused, and by-products of hydrogenolysis of hydroxyl in menthol is rarely produced, thereby preventing the generation of hydrocarbons which can not be repeatedly used. The hydrogenation reaction is carried out under low pressure, the reaction temperature is low, so requirement for the reaction equipment is not high; and the operating conditions is mild, thereby reducing the overall cost, and making the whole reaction process more environmental and safe. The thymol conversion rate is of 99.99%, and the yield is greater than 99%.

Description

technical field [0001] The invention belongs to the field of organic synthesis, and in particular relates to a synthesis method of d,l-menthol and several stereoisomers thereof. Background technique [0002] As a naturally occurring cyclic terpene alcohol, L-menthol is one of the main components of peppermint oil; due to its cooling and cooling effects, it is widely used in spices and seasonings, and is also widely used in medicine. d, l-menthol and its several stereoisomers d, l-neomenthol, d, l-isomenthol and d, l-neomenthol smell and taste slightly weaker than L-menthol, so Their synthesis has always attracted extensive attention. Separating them to obtain racemic d, l-menthol and its several isomers is also widely used as a cool and refreshing essence. [0003] Compounds with a menthane carbon skeleton containing at least one double bond and an oxygen atom connected at the 3-position, such as thymol, can be catalytically hydrogenated under a catalyst and a certain pres...

Claims

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Application Information

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IPC IPC(8): C07C35/12C07C29/20B01J25/02
Inventor 黄战鏖侯峰张长征钱正刚陈文杰
Owner 江苏宏邦化工科技有限公司
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