Ultrapure 4-methylpyrazole
View Patent ↗Disclosed is an ultrapure 4-methylpyrazole containing less than 0.1% pyrazole and containing less than 10 ppm each of hydrazine and nitrobenzaldehyde. The ultrapure 4-methylpyrazole is prepared by a novel process so that less than 0.01% of ethylvinyl ether is present.
1. A solution containing 4-methyl pyrazole containing less than 0.1% pyrazole.
2. The solution of claim 1 containing less than 10 ppm each of hydrazine and nitrobenzaldehyde.
3. The solution of claim 2 , wherein the nitrobenzaldehyde is p-nitrobenzaldehyde.
4. A process of making 4-methylpyrazole containing less than 0.1% pyrazole comprising the steps:
(a) reacting propionaldehyde with triethyl orthoformate to produce 1,1-diethoxypropane;
(b) reacting the 1,1-diethoxypropane of step (a) with an amine and an acid at a temperature of about 140-160° C. to produce 1-ethoxy-1-propene;
(c) washing the 1-ethoxy-1-propene with water and drying it without distillation;
(d) reacting the dried 1-ethoxy-1-propene of step (c) with triethyl orthoformate in the presence of a catalytic amount of boron trifluoride-diethyl etherate to produce 1,1,3,3-tetraethoxy-2-methylpropane; and
(e) reacting the 1,1,3,3-tetraethoxy-2-methylpropane of step (d) with hydrazine or a hydrazonium salt to produce 4-methylpyrazole containing less than 0.1% pyrazole.
5. A process of making 4-methylpyrazole containing less than 0.1% pyrazole and less than 10 ppm each of hydrazine and nitrobenzaldehyde comprising the steps:
(a) reacting propionaldehyde with triethyl orthoformate to produce 1,1-diethoxypropane;
(b) reacting the 1,1-diethoxypropane of step (a) with an amine and an acid at a temperature of about 140-160° C. to produce 1-ethoxy-1-propene;
(c) washing the 1-ethoxy-1-propene with water and drying it without distillation;
(d) reacting the dried 1-ethoxy-1-propene of step (c) with triethyl orthoformate in the presence of a catalytic amount of boron trifluoride-diethyl etherate to produce 1,1,3,3-tetraethoxy-2-methylpropane; and
(e) reacting the 1,1,3,3-tetraethoxy-2-methylpropane of step (d) with hydrazine or a hydrazonium salt to produce 4-methylpyrazole containing less than 0.1% pyrazole and less than 10 ppm each of hydrazine and nitrobenzaldehyde.
6. The process of claim 4 or 5 wherein the molar ratio of acid to amine is about 1:0.4-0.6.
7. The process of claim 6 wherein the reaction temperature is about 160° C.
8. The process of claim 4 or 5 wherein the 1-ethoxy-1-propene of step (b) is dried over a drying agent in step (c).
9. The process of claim 8 wherein the drying agent is magnesium sulfate.
10. The process of claim 4 or 5 wherein the dried 1-ethoxy-1-propene of step (c) contains less than 0.01% ethylvinyl ether.
11. The process of claim 10 wherein less than 0.01% ethylvinyl ether is present in the dried 1-ethoxy-1-propene of step (c) as a result of the molar ratio of acid to amine, the reaction temperature, and the washing and drying of the product without distillation.
12. The process of claim 4 or 5 wherein in step (e) a slight molar excess of 1,1,3,3-tetraethoxy-2-methylpropane is used relative to the hydrazine or hydrazonium salt.
13. The process of claim 12 wherein the molar excess is about 0.1% to about 0.5%.
14. The process of any one of claims 4 , 5 or 12 wherein a hydrazonium salt is used in step (e).
15. The process of claim 14 wherein the hydrazonium salt is hydrazine hydrosulfate.
16. A composition consisting essentially of 4-methyl pyrazole containing less than 0.1% pyrazole.