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

The gas phase reaction I 2 + HCOOCH 3 → HI + CH 3 I + CO 2 has been studied spectrophotometrically in a static system over the pressure ranges I 2 (6–39 torr) and HCOOMe (28–360 torr). In the temperature range 293–356°, the initial rate of disappearance of I 2 is first order in [HCOOMe] and half‐order in [I 2 ]. The rate determining step is equation image where k 1 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.