DE1593404B - Process for the preparation of methallyl esters. Eliminated from: 1246714 - Google Patents

Description

A process for the preparation of methallyl esters of the general formula was found

O CH ₃ R ₂

R ₁ -CO-CH ₂ -C = C

(D

15th

in which R ₁ , R ₂ and R _{3 have} the meaning given above, ^{heated to 400 to 600 °} C. with a dwell time of 1 to 200 seconds.

Aryl radicals are substituted to / f-alkoxyaldehydes according to the following scheme:

R '0-CH ₂ R "'

C C

R "0-CH ₂ R""

R '"

► R'R-CHO - CH ₂ - C - CHO

R ""

This isomerization is carried out between 250 and 550 ^° C. using pumice stone or certain silicas as a catalyst.

It has surprisingly been found that the reaction takes a completely different course and leads to methhallyl alcohol esters of structure (I), and that in addition the presence of a catalyst is optional if the 5-formation is occupied by an alkylidene substituent and at least one of the substituents in the 2-position is a hydrogen atom.

The starting products used for the process according to the invention MelhyIen-5-m-dioxanes can prepared in a known manner from a corresponding aldehyde and a corresponding diol will. They can also be obtained by pyrolysis of diene compounds according to the following reaction will:

35

O -CH,

R ₇

C = C

0-CH ₂

(H)

R ₁

Q-CH ₂

R,

H 0-CH ₂ DR ₃

40

wherein R ₁ , R ₂ and R _{3 are} hydrogen or aliphatic, alicyclic, aromatic or heterocyclic radicals, found, which is characterized in that a methylene-5-m-dioxane of the general formula

R ₁ O-CH ₂

(D) + C C = C

R,

H Q-CH ₂

R ₃

55

wherein R ₁ , R ₂ and R _{3 have} the meaning given above, heated to 400 to 600 ° C with a residence time of 1 to 200 seconds.

The preparation of methallyl esters by the known method of esterification of the corresponding Alcohols with an organic acid in the presence of a strong one serving as a catalyst Mineral acid generally leads to moderate results, due to the strong tendency of the methallyl alcohols, to isomerize to isomeric saturated aldehydes.

The isomerization of m-dioxanes, which are in the 5-position with two alkyl or wherein D represents a divalent radical obtained by addition of a conjugated diene (D) of the following called type arises from a double bond. Suitable compounds D are, for example

a) open chain conjugated diolefins, e.g. B. butadiene, isoprene, piperylene, dimethyl-2,3-butadiene;

b) alicyclic or heterocyclic conjugated diolefins, e.g. B. Cyclopentadiene and its alkyl derivatives, 1,3-cyclohexadiene or furan;

c) anthracene or its derivatives, naphthacene or other polycyclic aromatic compounds, which are known to react as diene components in the Diels-Alder reaction.

It has been found that the m-dioxanes of the formula (II) isomerize under the sole action of temperature. The isomerization is preferably carried out from 420 to 500 ⁰ C.

The reaction is carried out in the vapor phase at normal pressure or under reduced pressure.

5 can also be used under overpressure, however, this does not have any particular advantages, ie the vapors of the methylene-5-m-dioxanes can be carried along nem inert gas, e.g. B. nitrogen or carbonic acid can be diluted. A residence time of about 10 to 0 seconds is appropriate.

The reactor can, for example, be a tube made of a material that is resistant to the temperatures used, e.g. B. made of Pyrex, las, steel, stainless steel, nickel, or a 4onelalloy. It can be empty or filled with materials that promote heat exchange, for example with balls or rings made of glass, porcelain, or stainless steel. Grains made from kieselguhr, pumice stone, kaolin or other compounds containing silicon dioxide can also be used. The pipe filling can be arranged as a fixed bed or as a fluidized bed.

The vapors of the pyrolysate are condensed at the exit of the reactor. The ingredients will separated in a known manner, for example by direct rectification. The unconverted Diopanal is returned to the reactor.

The methallyl esters prepared by the process according to the invention can be ethylenic with others Monomers are polymerized or copolymerized and are therefore interesting starting materials for the production of a wide variety of polymers and synthetic resins.

example

The methallyl esters listed in the table below were obtained by isomerizing the corresponding methylene-5-m-dioxane according to the reaction

O — CH,

/ \
H Q-CH ₂

CH,

> RCOOCH ₂ - C = CH ₂

produced as follows: A reactor was used which consisted of a U-tube made of stainless steel 450 mm long and 17 mm inside diameter. The tube was ^{filled with 70 cm 3 of} pumice stone grains of 2 to 4 mm and immersed in a molten salt heated to 450 to 460C. It was connected at one end to a calibrated dropping funnel and a nitrogen source and at the other end to a water-cooled condenser and traps cooled with ice and solid carbon dioxide to collect the pyrolysate. For each test of the test series listed in the table below, amounts of 150 g were used. The starting substance differed in each case by the remainder R, which was varied as indicated in the table. The starting compound was introduced into the tube in each case in an amount of 50 g / hour with a nitrogen flow of about 10 liters / hour.

The pyrolysates were analyzed by gas chromatography, and conversion and yields were determined from the analysis. The results are in the following Table compiled. The pyrolysates were further fractionated into the methallyl ester decomposed, which were characterized by their infrared spectrum and their mass spectrum. Further the structure was determined by saponification of the benzoic acid esters and isobutyric acid esters and characterization identified the methallyl alcohols and benzoic acid and isobutyric acid obtained.

15th R. H Manufactured total yield (CH ₃ J ₂ CH - Mclhallyl ester sales of on CH ₂ = CH- correspond Methallyl CH ₂ = C (CH ₃ ) - related ester **) / \ / Methylene * υ I Formate 5-m-di- % 20th \ / Isobutyrate oxane *) 61.6 σ Acrylate 26th 97.6 Methacrylate 42 25.8 25th Cyclohexene 73.5. 39.2 3-carboxylate 92 ■ 88 Benzoate 33 30th 79.5 58.5

_t Amount used - Amount recovered
Amount used

Amount of ester formed in moles
Converted amount of dioxane in moles *

The methallyl isobutyrate obtained had the following key figures:

Boiling point 150 ° C / 20 mm

(Literature value
146 to 155 ° C)

Refractive index Yi ⁷ S 1.417

(Literature value
1.4174)

Density d? 0.884

The methallyl benzoate obtained had the following key figures:

Boiling point 101 to 102 ° C

Refractive index n ^} S 1.5145

Density d ² ? 1.0345

The isobutyric acid obtained by saponifying the first ester formed an S-benzylisothiuronium salt with a melting point of 143 ° C (literature value 142 to 142.5 ° C). The benzoic acid obtained from the second ester had a melting point of 122.4 ° C. Its mixture with an authentic benzoic acid sample did not result in a lowering of the melting point.

Claims (1)

Claim: Process for the preparation of methallyl esters of the general formula CH ₃ R ₂ R ₁ -CO-CH ₂ -C = C R3 where R ₁ , R ₂ and R _{3 are} hydrogen or aliphatic, alicyclic, aromatic or heterocyclic radicals, characterized in that a methylene-5-m-dioxane of the general formula O — CH, O — CH, C = C