Given the following heats of combustion per CH₂ group within the structure, which cyclic alkane has essentially no angle strain? (Ref: long-chain Alkane = 659 kJ/mol)

A) cyclobutane = 686 kJ/mol
B) cyclopentane = 664 kJ/mol
C) cyclohexane = 659 kJ/mol
D) cycloheptane = 662 kJ/mol
E) cyclooctane = 663 kJ/mol

Angle strain occurs when bond angles deviate from the ideal angles (109.5° for sp3 hybridization) in cyclic structures. The more deviated the bond angles, the higher the angle strain and energy required to maintain the structure.
In cyclic alkanes, the angle strain is directly proportional to the number of carbons in the ring. The larger the ring, the more strained the structure becomes, and the higher the energy required for combustion.
Of the given choices, cyclohexane has the lowest heat of combustion (659 kJ/mol), indicating that it has the least amount of angle strain. Therefore, the best choice is C.