A compound with molecular formula C₄H₁₀O is a functional isomer of CH₃CH₂CH₂CH₂OH and lacks a hydroxyl group. What is it
CH₃CH₂CH₂CH₂OH (butan-1-ol) is an alcohol. Its functional isomer without -OH is CH₃CH₂OCH₂CH₃ (diethyl ether), an ether.
Ref: NCERT Class 11 Chemistry > Chapter 8: Organic Chemistry - Some Basic Principles and Techniques > Topic: Classification and Nomenclature of Organic Compounds - IUPAC