Phthalide（Cat No.:R061044）, also known as isobenzofuran-1(3H)-one, is an aromatic lactone with the molecular formula C8H6O2. It consists of a benzene ring fused to a five-membered lactone ring, forming a rigid bicyclic structure. Phthalide appears as a white crystalline solid with a faint aromatic odor and is naturally found in certain plant species, including celery and lovage, contributing to their characteristic aroma. It serves as a valuable intermediate in the synthesis of pharmaceuticals, fragrances, agrochemicals, and dyes. Its reactive lactone ring makes it useful in forming heterocycles and functionalized aromatic compounds in organic synthesis.