H–D Exchange between methane and deuteriated potassium amide supported on alumina

Abstract

The H–D exchange reaction between methane and deuteriated potassium amide supported on alumina (KND₂/Al₂O₃), a strongly basic catalyst, has been investigated by FTIR spectroscopy. KND₂/Al₂O₃ was prepared by contacting KNH₂/Al₂O₃ with D₂ at 373 K for 30 min. The N–D asymmetric and symmetric bands in KND₂ were observed at 2411 and 2343 cm⁻¹. The ND₂ bending bands were observed at 1132 cm⁻¹. The H–D exchange reaction between CH₄ and KND₂ proceeded at room temperature. First, the N–H bands in KNDH were observed at 3210 cm⁻¹. and then KNDH was further converted to KNH₂, whose N–H stretching bands were observed at 3238 and 3190 cm⁻¹. The H–D exchange reaction between ethane and KND₂/Al₂O₃ also proceeded at room temperature, but the rate was slower than that between methane and KND₂/Al₂O₃. The lower reactivity of ethane indicates a carbanion mechanism since the acidity (pK_a) of ethane (42) is lower than that of methane (40).