Monolayers of i-propanol ((CH3)(2)CH-OH) were adsorbed at 125 K on gra
phite covered Pt(111) single crystal surfaces and subjected to fluxes
of thermal H atoms. The mechanisms of the reactions of i-propanol (OH,
OD) with H(D) atoms were investigated with thermal desorption spectro
scopy (TDS). The initial reaction step is an Eley-Rideal-type H abstra
ction at the secondary CH group to form the i-propyl radical ((CH3)(2)
C .-OH). This reaction proceeds with an apparent cross-section of abou
t 1.5 Angstrom(2). Impact of a further H(D) atom can transfer the radi
cal via a second H abstraction reaction at the OH group into acetone (
(CH3)(2)C=0). Accordingly, the overall reaction consists of oxidation
of i-propanol to acetone, Alternatively, i-propanol is restored from t
he radical via H addition to the radical carbon centre. Likewise, adso
rbed acetone is transferred into i-propanol by H impact. The presence
of the OH group in the target molecule i-propanol enhances the abstrac
tion reaction cross-section at the CH group by a factor of about five
as compared to abstraction from CH2,3 groups of physisorbed alkanes.