JPH0314526A - Production of n-alkylbenzene - Google Patents

Abstract

PURPOSE:To obtain the subject substance useful as precursor of raw material of liquid crystal in high yield and with simple post-treatment by reacting phenyl Grignard reagent and aldehyde to obtain non-phenyl alcohol and decomposing resultant substance with hydrogenation. CONSTITUTION:A compound expressed by formula I (X is halogen) is reacted with a compound expressed by formula II (R is 2-5C linear alkyl) in a solvent such as diethyl ether at 0-70 deg.C for 15min to 2hr and an acidic aqueous solution is added to reacted solution, then extracted with ether or benzene, etc., to obtain a compound expressed by formula III. Next, catalyst such as Pd/C or Rh/C, etc., is used in an amount of 0.01-10wt.% of the compound expressed by formula III and the compound expressed by formula III is subjected to hydrogenating decomposition reaction in a solvent such as methanol at 0-100 deg.C under 0-20kg/cm<2> hydrogen pressure for 0.2-5hr to afford a compound expressed by formula IV. Any waste water is not generated because AlCl3 catalyst is not use, and post-treatment is readily performed.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a method for producing n-alkylbenzene,
More specifically, the present invention relates to a method for producing n-alkylbenzene useful as a precursor for, for example, a liquid crystal raw material, in which n-alkylbenzene can be efficiently produced in a high yield, and in which post-processing is simple. [Prior art and problems to be solved by the invention] In recent years,
Various liquid crystals made of liquid organic compounds with optical anisotropy such as cholesteryl benzoate have been developed. In the liquid crystal made of this liquid organic compound,
N-alkylbenzene, which is one of the precursors of liquid crystals, is sometimes used as a manufacturing raw material. As a method for producing this n-alkylbenzene, for example, linear carboxylic acid chlorite and benzene are acylated by a Friedel-Crafts reaction in the presence of an alkyl chloride catalyst to obtain an n-alkyl ketone. There is a known method for producing n-alkylbenzene by subsequently reducing this n-alkylketone using a reducing agent (KOH◆Ntun) (see U.S. Pat. No. 3,697,594).
．． However, in this production method, there are many side reactions and it is difficult to separate the isomers produced at the same time, so there is a problem that n-alkylbenzene cannot be obtained efficiently with a sufficiently high yield. In addition, since an aluminum chloride catalyst is used, wastewater containing this aluminum chloride catalyst is generated, making wastewater treatment complicated. This invention was made based on the above circumstances. That is, an object of the present invention is to provide a method for producing n-alkylbenzene that can efficiently produce n-alkylbenzene with a high yield and that allows for simple post-processing. [Means for Solving Problem W1] In order to solve the above problem, the inventor has made extensive studies and found that a specific method for hydrogenolyzing a specific compound obtained by reacting specific raw materials. They discovered that n-alkylbenzene can be obtained efficiently in high yield and that the post-treatment is simple, leading to the present invention. The structure of this invention is as follows: (1) In the following formula [I], X represents a halogen atom. ] A phenyl Grignard reagent represented by the following formula [I1]
．． RCHO [II] (1) The following formula [nl, R represents a straight alkyl group having 2 to 5 carbon atoms. ] A method for producing n-alkylbenzene, which comprises reacting with an aldehyde represented by the following to obtain l-phenyl alcohol, and then hydrogenolyzing the l-phenyl alcohol. In the production method of this invention, ■First, the following reaction formula (
1111) to react the phenyl Grignard reagent represented by the formula [I] with the aldehyde represented by the formula [I1] to obtain l-phenyl alcohol. (However, X represents a halogen atom, and R has 2 to 2 carbon atoms.
5 represents a linear alkyl group. ) ■ Next, a hydrogenolysis reaction represented by the following reaction formula (IV) is carried out,
The l-phenyl alcohol obtained by the Grignard reaction is hydrogenolyzed. 0H (However, R represents a linear alkyl group having 2 to 5 carbon atoms.) The production method of the present invention will be explained below in the order of the Grignard reaction and the hydrogenolysis reaction. - Grignard Reaction - In the production method of the present invention, first, the phenyl Grignard reagent represented by the above formula [I] is reacted with the aldehyde represented by the above formula [1] using the Grignard reaction, thereby producing l-phenyl. Get alcohol. The phenyl Grignard reagent represented by the formula [N can be obtained, for example, by reacting halogenated benzene and metallic magnesium in a solvent such as anhydrous ether. In the method of the present invention, among the phenyl Grignard reagents represented by the formula [I], phenyl Grignard reagents obtained from the reaction of bromobenzene and metallic magnesium can be particularly preferably used. Specifically, the aldehyde represented by the formula [01] includes n-probilaldehyde, n-butyraldehyde, n-butyraldehyde, and n-butyraldehyde.
-Benzylaldehyde, n-hexylaldehyde, etc. In the method of the present invention, among the aldehydes represented by the formula [1], n-probilaldehyde, n-butyraldehyde, n-bentyraldehyde, and n-hexylaldehyde can be particularly preferably used. The Grignard reaction expressed in the above reaction formula [ml] is an equimolar reaction, but the above reaction formula [I] in the method of this invention
The ratio of the phenyl Grignard reagent represented by the formula [■] to the aldehyde represented by the formula [■] is usually 0.7 to 1.1 mol of the phenyl Grignard reagent to 1 mole of the phenyl Grignard reagent. 2 mol, preferably 0.8 to 1.0 mol. The solvent (hereinafter sometimes referred to as solvent A) used in the Grignard reaction expressed in the reaction formula [ml] may be any solvent that is stable for this reaction.
There are no particular limitations; for example, a solvent similar to that used for preparing the Grignard reagent can be used. Specifically, diethyl ether, dibrobyl ether,
Examples include dibutyl ether, dioxane, furan, tetrahydrofuran, cineole, and diethylene glycol dimethyl ether. The amount of the solvent A used in this reaction is usually 0.1 to IOf per 1 mole of the phenyl Grignard reagent.
L. Preferably it is 0.1 to 3 sentences. The reaction temperature of the Grignard reaction is usually set at -78 to 70°C, preferably 0 to 70°C. Further, the pressure in this Grignard reaction may be normal pressure, increased pressure, or reduced pressure, but in the method of this invention, it is preferable to carry out this reaction under normal pressure. The reaction time of the Grignard reaction is usually 5 minutes to 5 hours, preferably 15 minutes to 2 hours. In the method of the present invention, after the Grignard reaction is completed, a post-treatment is usually performed to obtain the l-phenyl alcohol. This post-processing can be performed, for example, as follows. That is, add an acidic aqueous solution such as sulfuric acid or hydrochloric acid to the resulting reaction solution. Next, ether, benzene, toluene,
Extract the reaction product with ethyl acetate, etc. Neutralize the obtained extract, wash with water, and separate the organic layer of this liquid. By performing a concentration operation such as distillation or evaporation on this organic layer, l-phenyl alcohol can be obtained, and the recovered solvent can be reused. In the method of this invention, after 1-phenyl alcohol is obtained as described above, this 1-phenyl alcohol is hydrogenolyzed using the hydrogenolysis reaction described in detail below. - Hydrogenolysis reaction - In the hydrogenolysis reaction of l-phenyl alcohol in the method of the present invention, a catalyst is usually used. The catalyst is not particularly limited as long as it is a hydrogenolysis catalyst, and specifically, palladium. Carbon (Pd/C
) catalysts such as palladium catalysts, platinum catalysts such as platinum black (pt) catalysts, nickel catalysts such as Raney nickel and precipitated nickel, cobalt catalysts such as Raney cobalt and precipitated cobalt, copper catalysts, copper chromate catalysts, molybdenum sulfide catalysts, cobalt sulfide Catalyst, rhodium carbon (R
h/C) catalysts, etc.

Among these various hydrocracking catalysts, preferred are palladium catalysts such as palladium/carbon (Pd/C) catalysts and rhodium/carbon (Rh/C) catalysts. The amount of the catalyst to be used in the hydrogenolysis reaction cannot be uniformly prescribed because it differs depending on the type of catalyst, but it is usually . 0.
The amount is about 01 to 10% by weight. The solvent used in the hydrogenolysis reaction (hereinafter sometimes referred to as solvent B) is preferably a solvent that is inert to the hydrogenolysis reaction and stable to the hydrogenolysis reaction. Specific examples include alcohols such as methanol, ethanol, and propanol, aliphatic hydrocarbons such as n-hexane and n-hebutane, and aromatic hydrocarbons such as benzene, toluene, and xylene. It is also possible to use a mixture of these solvents in an appropriate combination. The amount of the solvent B used is usually 30 parts by weight or less, preferably 20 parts by weight or less, based on l-phenyl alcohol.The reaction temperature in the hydrogenolysis reaction is usually 2 parts by weight or less.
℃, preferably 0 to 100℃. The hydrogen pressure in the hydrogenolysis reaction is usually 0 to 50℃.
kg/am”, preferably O ~ 20 kg/c
In addition, the reaction time of the hydrogenolysis reaction is usually set to 0.2 to I
O hours, preferably 0.2 to 5 hours. In the method of the present invention, after the hydrogenolysis reaction is completed, a post-treatment is usually carried out to separate the solvent and the product (n-alkylbenzene). After separating the catalyst from the resulting reaction solution, the solvent and product (n-alkylbenzene) can be easily separated by distillation etc.Then, the recovered solvent can be reused. As described above, according to the manufacturing method of the present invention, n-
Alkylbenzene can be obtained easily and efficiently with a high yield, and since wastewater containing catalysts such as aluminum chloride is not generated, subsequent treatment can be carried out easily. Also. The n-alkylbenzene produced by the method of the present invention can be suitably used, for example, as a precursor that is a liquid crystal raw material. An example of synthesizing a liquid crystal material from this n-alkylbenzene is shown below. The crystalline Th substance is not limited to the compound represented by the above formula, but includes various other compounds. υ Note that liquids that can be synthesized from n-alkylbenzene [Examples] Next, examples and comparative examples of the present invention will be shown to further specifically explain the present invention. (Examples 1 to 7) In a reaction vessel equipped with a phenyl thermometer, a cooling tube, and a dropping funnel,
Magnesium metal (1.215 g, 0.05 mol) was added, and the solvent shown in Table 1 was added to cover the magnesium. Bromobenzene (0.05 mol) was added to the dropping funnel, the cock of the dropping funnel was opened, and a small amount of bromobenzene was added to the reaction vessel. When the reaction vessel was slightly heated, it generated heat, confirming that the reaction had started. Furthermore, the remaining bromobenzene was added dropwise over about 20 minutes. At this time, heat generation occurred, so the temperature was maintained at the predetermined temperature shown in Table 1 by water cooling. After dropping bromobenzene, the mixture was heated for 20 minutes at the reaction temperature shown in Table 1. After the reaction vessel was allowed to cool, the aldehydes shown in Table 1 (O.OS mol) were added dropwise into the reaction vessel from the dropping funnel over a period of about 20 minutes. At this time, a large amount of heat was generated, so the reaction temperature was maintained at the predetermined temperature shown in Table 1 by water cooling. After dropping, let cool and add sulfuric acid aqueous solution (3gHtsOs/30m
The reaction was stopped by gradually adding Ko 11.0) to the reaction solution. The reaction solution was extracted with ether (50mJIX 3 times), and the ether layer was extracted with NaHCO, an aqueous solution (:+o
After neutralization with water (30 mJL), washing with water (water, 30 mJL), dehydration with anhydrous NatSO, and further concentration, the corresponding crude l-
Phenyl alcohol was obtained.丞1 {1, KOH} The obtained crude l-phenyl alcohol Ig, 5 ml of the solvent shown in Table 1, and 0.01 g of the catalyst shown in Table 1 were each placed in a 30 cc autoclave. The reaction was carried out at the specified hydrogen pressure, reaction temperature, and reaction time shown in the table. After the reaction, the reaction products obtained were analyzed by gas chromatography, and it was confirmed that the corresponding n-alkylbenzenes shown in Table 1 were obtained at the yields shown in Table 1. ．． (Comparative Example) Free-Luke Crafts Benzene (40ml) and Aluminum Chloride (6ml)
．． 67 g, 0.05 mol) was placed in a 100 mJ 12-necked flask equipped with a dropping funnel and a thermometer. Also, put propionic acid chlorite into the dropping funnel, and cool the reaction vessel so that the reaction temperature is 30 to 35°C.
It was dripped over about 20 minutes. After dropping, let it cool and lower the temperature to 3.
The mixture was brought to 0°C and stirred for 1 hour. Next, add 10mJl of water and extract with benzene (50ml
JIXa times), further neutralize the separated benzene layer,
Then I washed it with water. Thereafter, the benzene layer was diluted with anhydrous Na. After drying with SOn and concentrating, oil Ii. 75g was obtained. Oil obtained from the above Friedel-Kraf reaction 6.7
5g of potassium hydroxide and 14g of potassium hydroxide in 50ml of 2-(2-ethoxyethoxyl) ethanol,
Add 99% hydrazine llg (
The oil was reduced by adding 0.22 mol) and reacting at a temperature of 135°C for 4 hours. After the reaction, the reaction solution was poured into a 200 ml wood, and benzene extraction (100 mi x 3 times) was performed. When this benzene layer was analyzed by gas chromatography, it was confirmed that n-propylbenzene was obtained with a yield of 80%. (Evaluation) As is clear from Table 1, in all Examples,
It was confirmed that n-alkylbenzene could be produced in a higher yield than in the comparative example. In addition, in the examples, since aluminum chloride was not used as a catalyst, no wastewater containing aluminum chloride catalyst was generated.
Post-processing was simple. It is possible to provide an industrially useful method for producing n-alkylbenzene having the following advantages.

[Effects of the Invention] According to the present invention, (+) Hydrogenolysis of 1-phenyl alcohol obtained by carrying out a Grignard reaction using a specific Grignard reagent and a specific aldehyde is utilized, so it can be used as a precursor for liquid crystal raw materials, for example. (2) Since no aluminum chloride catalyst is used, no wastewater is generated due to the aluminum chloride catalyst, and post-treatment is convenient. is,

Claims (1)

[Claims] (1) Following formula [I]; ▲ Contains mathematical formulas, chemical formulas, tables, etc. ▼
[I] [However, in the formula [I], X represents a halogen atom.
] A phenyl Grignard reagent represented by the following formula [II]; RCHO[II] [In formula [II], R represents a straight-chain alkyl group having 2 to 5 carbon atoms. ] A method for producing n-alkylbenzene, which comprises reacting the 1-phenyl alcohol with an aldehyde represented by the formula to obtain 1-phenyl alcohol, and then hydrogenolyzing the 1-phenyl alcohol.