Carboxymethyl guar gum (CMGG) synthesized via Friedel CraftAcylation using FeCl3 and AlCl3 as Friedel Craft catalyst. Also the effect of phase transfer catalyst tetra ethyl ammonium bromide (TEAB) on the degree of substitution (DS) was monitored. The reaction parameter like temperature, reaction time etc. was optimized. The DS of reaction product wasmeasured byAmberlite IRA96 anion exchange resin.MaximumDS of 0.7was obtained. CMGGwas characterized byFourierTransformInfrared spectroscopy (FTIR).