Process for making tricyclodecenyl esters
A practical, economical process for making tricyclodecenyl esters is disclosed. After reacting a lower carboxylic acid and a dicyclopentadiene in the presence of triflic acid to form the ester, the reaction mixture is distilled in the presence of a base to isolate a fragrance-quality tricyclodecenyl ester. Adding enough base to neutralize the triflic acid enables a distillation-only purification, facilitates starting material recovery, and avoids drawbacks of a basic workup.
1. A process comprising: (a) reacting a C 2 -C 4 carboxylic acid and a dicyclopentadiene at a carboxylic acid:dicyclopentadiene molar ratio within the range of 0.8 to 1.3 in the presence of triflic acid to produce a tricyclodecenyl ester; and (b) distilling the reaction mixture in the presence of 1 to 1.5 equivalents, based on the amount of triflic acid, of a base to isolate the tricyclodecenyl ester from unreacted dicyclopentadiene and unreacted carboxylic acid.
2. The process of claim 1 wherein the unreacted dicyclopentadiene, unreacted C 2 -C 4 carboxylic acid, or both are recovered and used in a subsequent reaction to make additional tricyclodecenyl ester.
3. The process of claim 1 wherein at least a portion of the C 2 -C 4 carboxylic acid is generated by hydrolyzing an acyclic anhydride corresponding to the C 2 -C 4 carboxylic acid with water in the presence of triflic acid.
4. The process of claim 1 wherein the distillation is performed in the presence of 1.0 to 1.1 equivalents of the base.
5. The process of claim 1 wherein the base is selected from the group consisting of ammonium, alkali metal, and alkaline earth metal hydroxides, oxides, alkoxides, carbonates, bicarbonates, carboxylates, phosphates, sulfates, nitrates, halides, and mixtures thereof.
6. The process of claim 1 wherein the dicyclopentadiene is unsubstituted dicyclopentadiene (DCPD).
7. The process of claim 6 wherein the dicyclopentadiene has a purity within the range of 80 to 90%.
8. The process of claim 1 wherein the distilled tricyclodecenyl ester is a commercially acceptable fragrance component.
9. The process of claim 1 wherein the C 2 -C 4 carboxylic acid is selected from the group consisting of acetic, propionic, n-butyric, and isobutyric acids.
10. The process of claim 1 wherein the C 2 -C 4 carboxylic acid is acetic acid, the dicyclopentadiene is DCPD, and the tricyclodecenyl ester is tricyclodecenyl acetate (TCDA).
11. The process of claim 10 wherein the DCPD is added gradually to a mixture comprising acetic acid and triflic acid.
12. The process of claim 10 wherein the distilled tricyclodecenyl ester comprises at least 95 wt. % of TCDA isomers.
13. The process of claim 12 wherein the distilled ester comprises at least 98 wt. % of TCDA isomers.
14. The process of claim 12 wherein the distilled ester has an index of refraction (n D 20 ) within the range of 1.49 to 1.50.
15. The process of claim 12 wherein the distilled ester has a relative density (d 4 20 ) within the range of 1.07 to 1.08.
16. The process of claim 1 wherein the carboxylic acid:dicyclopentadiene molar ratio is within the range of 0.9 to 1.1.
17. The process of claim 1 wherein the amount of triflic acid is less than 1 wt. % based on the amount of the dicyclopentadiene.
18. The process of claim 1 wherein the reaction is performed at a temperature within the range of 60° C. to 150° C.
19. The process of claim 1 wherein the reaction is performed at a temperature within the range of 110° C. to 140° C.
20. The process of claim 1 performed in batch, semi-continuous, or continuous mode.