CH2COOH

CH2COOH is commonly referred to as the carboxymethyl group, a two-carbon functional moiety consisting of a methylene group (-CH2-) linked to a carboxyl group (-COOH). When attached to a larger molecule, it is often written as -CH2-COOH, forming the carboxymethyl substituent. The chemical formula for this substituent is C2H3O2.

In terms of structure and properties, the carboxyl group provides acidity, allowing deprotonation in water to form a carboxylate (-COO−). The group is polar and hydrophilic due to the carboxylate, while the methylene bridge offers some flexibility in the attached molecule. The carboxyl group typically has a pKa in the range of about 4.5, similar to acetic acid, though the exact acidity can vary with substitution and environment.

Occurrence and applications of the carboxymethyl group are widespread in chemistry and biochemistry. In biochemistry, the motif is present in amino acids such as glycine (NH2-CH2-COOH), where the carboxymethyl fragment is part of the molecule. In industrial chemistry, the group is used to make carboxymethyl derivatives such as carboxymethyl cellulose (CMC). In CMC, cellulose hydroxyl groups are etherified with monochloroacetic acid to yield cellulose chains bearing -CH2-COONa groups, enhancing solubility and charge properties. The carboxymethyl moiety also serves as a versatile handle for further derivatization, enabling formation of esters, amides, and other functionalized compounds.

Synthesis and handling of materials bearing the carboxymethyl group typically involve alkylation or etherification reactions under basic conditions, with the resulting products existing in salt or neutral forms depending on the reaction medium and counterions.