SU713857A1 - Method of preparing 1,2-methylcyclopentadienes - Google Patents

Description

This invention relates to methods for producing 1,2-methylcyclopentadienes Methyl. Cyclopentadiene homologues can be used in the synthesis of pre-chemicals and anti-knockers. A method is known for producing 1-g-methylcyclopentadienes by decomposing alkenyldioxanes-1.3 at 50-600 ° C and pressure 1002200 mm Hg in the presence of L1J acid catalyst. Target product yield 14.839, 1%. The disadvantage of the method is the low yield of the desired product. The closest to the invention on the achieved result is the method of obtaining 1,2-met ilcyclopent dienes by splitting 4-alkenyldioxane-1, 3 in the presence of water and chlorine at a temperature of 40-120 ° C and the ratio between 4-alkenyldioxane-1, 3, water and chlorine 1: 10-30:: 0.5-5 2 When decomposing 4-propenyl dioxane-1, 3, the yield of the target product is 82%. A significant disadvantage of the method is the use of chlorine as a catalyst (chlorine, aggressive, an additional step is required to obtain it). , 2-methylcyclopentadienes and simplification of the process technology. This goal is achieved by the method of producing 1-, 2-methylcyclopentadienes by cleaving 4-propenyl-2-K-1,3-dioxane, where R is alkyl, in the presence of an acid catalyst and water at elevated temperature. Preferably, the process is carried out at a temperature of 240 -270C and a volume ratio between 4-propenyl-2-R-1, 3-dioxane and water, equal to 1: 1.5-4. Orthophosphoric acid (H,) on silica gel (SG) or kieselgur (KG) is usually used as a catalyst. The difference is that 4-propenyl-2-R-1, 3-dioxanes are subjected to cleavage under preferred conditions. The starting 4-propenyl-2-E-1,3-dioxanes are obtained by condensation of aldehydes | of the formula RCHO, where C.y., H-CgH-j, iso-CdH (j, iso-CHn, formaldehyde and piperylene, The process was carried out at a feed rate of 0.4–2.0 hours to add 1–1.5 weight of orthophosphoric acid to water to prevent the catalyst from falling and cyclical activity. To obtain 1, 2-methylcyclopentadienes a flow system consisting of a tubular metal reactor with a length of 400 ivw and a diameter of 25 mm, the upper part of which is filled with glass bead mi serves as an evaporator and a superheater, and the lower part (reaction zone) is filled with a catalyst (contact) and placed in an electric furnace; microdosing pumps, and a system for receiving products, consisting of xoJtO dily-scale and a receiver equipped with a cooling jacket e p "4 Propenyl-2-K-1; 3-dioxane and a mixture of, with IAPO (11, 5 wt.%) podzgot E evaporator-g, r-" rotor heater. Couples brought to the temperature of experience contact with the layers the catalyst oObSNroM 30 cm, after which the contact gas flows through the cooler into the receiver. The catalyst is neutralized, for example, with ammonia, the organic phase is separated, dried, a small amount of hydroquinone (0.5-1%) is added and rectified (column 10-12 tons), to obtain a mixture of methylcyclopentadienes, b.p. b9-79 C; , 4598; , 8l80. Found,% C 89.81 H 10.11; MRt-b, 73. Introduce slender,%; C 89.94; H 10.06; MRY, 26.77 ,, The results are presented in the table;

8.50 240 3.50 H 260 8f50 270

 8.50 257 8f50 NDROD / KG 2ba 3.50 HgPqj / Kr 27.0 /, 82 Ilgpqj / KG 265 7, / iO, / KG 263

9.20

260

9,. 20 H, pq, 240

 / SG

20 270

d 9.20 258

7.1 263 7.82 N, RO, / SG 270 This method allows semi-addition of I-, 2-methylcyclopentadienes on its available petrochemical products; piperylene (waste of isoprene rubber), formaldegyl and aldehydogs (produced on a scale as it is) - with a high yield (up to 95%; 3%). Aldehydes,

used in the process can be applied many times.

Claims (2)

 1. A method of producing 1-, 2-methylcyclopentadienes by splitting 4-alkenyl dioxane-1,3 in the presence of an acid catalyst and water at a raised temperature, characterized in that, in order to increase the yield of the target product and simplify the process, as 4- alkenyl dioxane use 4-propenyl-2-H-1,3-dioxane, where R is alkyl 2. Method POP.1, characterized in that the process is conducted at a temperature of 240-270C and a volume ratio between 4-propenyl-2-R-1, 3-dioxane and water, equal to lsl, 5-4. 3, Method POP.1, characterized in that orthophosphoric acid on silica gel or kieselguhr is used as a catalyst, Sources of information taken into account in the examination 1. USSR author's certificate No. 387955, cl. C 07 C 13/14, C 07 C 1/20, 1971. 2. USSR author's certificate 5 №416337, cl. C 07 C 13/14, C 07 C 1/20, 1972 (prototype).