Table: 2.

Optimization of the crystallization solvent for effective removal of impurities of 4-(trifluoromethyl)benzohydrazide (7)^a.

Entry	Impurity content in Crude (%)	Titration bolvent (vol.)	Purification conditions	Yield of 7 (%)b	Purity of 7 (%)c	Impurity content in purified 7 (%)d
1	0.12	2 V Water	0.5 V methanol	65	86.72 %	0.09
2	0.12	4 V water	–	72	91.16 %	0.10
3	0.15	4 V Water	1 V methanol	67	89.97 %	0.08
4	0.14	4 V Water	2 V acetone	73	95.30 %	0.05
5	0.18	4V Water	0.5 V methanol	77	96.97 %	0.10
6	0.07	3 V Water	1 V MTBE	79	98.68 %	0.08
7	0.14	4 V Water	2 V MTBE	82	99.05 %	0.05
8	0.10	4 V Water	3 V MTBE	87	99.96 %	0.01
9	0.10	5 V Water	5 V MTBE	80	79.34 %	0.04

^aReaction conditions: 6 (1.0 eq), hydrazine hydrate as solvent (1.5 eq), reflux.

^bCalculated yields were given as isolated yields.

^cPurity determined by HPLC.

^dImpurity content in 7 determined by HPLC.