Carbon–hydrogen bond strengths in methyl formate and the kinetics of the reaction with iodine

The gas phase reaction I₂ + HCOOCH₃ → HI + CH₃I + CO₂ has been studied spectrophotometrically in a static system over the pressure ranges I₂ (6–39 torr) and HCOOMe (28–360 torr). In the temperature range 293–356°, the initial rate of disappearance of I₂ is first order in [HCOOMe] and half-order in [I₂]. The rate determining step is where k₁ is given by where θ = 2.303 RT in kcal/mole. This activation energy gives a carbonyl C? H bond strength of 92.7 kcal/mole. At 356° there was no evidence of abstraction of a methoxy hydrogen, so a lower limit of 100 kcal/mole may be placed on this C? H bond strength. These ester C? H bond strengths are discussed in relation to comparable values in aldehydes and ethers.