AbstractTwo reaction paths which can be followed when an acid chloride reacts with an alcohol are discussed. The role of pyridine as solvent and catalyst in this reaction is described. The importance of inductive and resonance effects and the size and arrangement of groups near the carbonyl are emphasized. The heterogeneous preparations of seven cellulose partial esters, the phenylacetate, benzoate, trimethylacetate, triphenylacetate, β,β,β‐triphenylpropionate, α‐(4‐biphenylyl)phenylacetate, and mesitoate are described. Pronounced interference with esterification is noted only in the preparation of the triphenylacetate. Steric hindrance and a poor ability to ionize are considered to be responsible for this result. Outstanding resistance to saponification, thought to be the result of steric hindrance and a reduced tendency to ionize, is reported for three of the cellulose esters, the triphenylacetate, the β,β,β‐triphenylpropionate, and