(+-)-2-n-Propyl-4-pentynoic acid 136321-95-4 2-Propyl-4-pentynoic acid 2-n-Propyl-4-pentin acid 2-n-Propyl-4-pentynoic acid 24102-11-2 4-Pentynoic acid, 2-propyl- 4-yn-VPA R,S-4-yn-VPA