Phthalide is an organic chemical compound with the molecular formula C8H6O2. It is a lactone that serves as the core chemical structure for a variety of more complex chemical compounds including dyes (such as phenolphthalein), fungicides (such as tetrachlorophthalide, often referred to simply as "phthalide"), and natural oils (such as butylphthalide).

Phthalide is used in the synthesis of several pharmaceutical drugs including isoxepac, vatalanib, and hydralazine as well as the pesticide kresoxim-methyl .

administered for three days at doses of 10 or 40

1. In checking these directions complete failure was repeatedly encountered with good commercial grades of zinc dust, and only when the metal was activated with copper sulfate did reduction proceed at all.

2. The mother liquor, on concentrating to less than half its volume, yields no further crystals on chilling.

3. On cooling, a minute amount of a yellow impurity separates with the phthalide at the beginning of crystallization. This impurity apparently cannot be eliminated by boiling with charcoal but is present in too small amount to affect the melting point of the product.

4. Concentration of the final mother liquor to a volume of 500 cc. yields a further small quantity of phthalide, but this operation is scarcely worth while.

PHTHALIDE FOR SYNTHESIS