3386
J . A m . Chem. SOC.1985, 107, 3386-3387
I1 is a strong base (vide infra) it reacts readily with I, so that maximum amounts of I1 arise at low conversions of reaction 1. Ion I1 reacts in a completely different manner from its isomer, acetaldehyde enolate (111). It is a strong base, and m / z 43 is converted completely into m / z 44 by reaction with D 2 0 (eq 2). CH,C=O
+
D,O
-[
]
. OD-
CH,-g-D O
(2)
I 0I
CH,=C-D III
+
HOD
It also undergoes addition reactions, for example with CO2.I6 CH,(?=O
+
CO,
-
CH,COCO,-
(8)
It seems likely that this method will prove general for the formation of acyl anions in the gas phase, and further investigations are currently in progress.
Acknowledgment. We gratefully acknowledge the support of this work by the National Science Foundation under Grant CHE-8203110 (to C.H.D. and V.M.B.) and Grant CHE-8313826 (to R.D.). Registry No. CH3CO-, 64723-93-9; (CH3),SiCOCH3, 1341 1-48-8; F, 16984-48-8; CHSCO, 31 70-69-2.
m/z 44
No DO- is produced in this reaction, which suggests that the first step is endothermic or thermoneutral and that I1 is less basic than hydroxide ion (AWadd(HzO)= 391 kcal/mol).I2 This conclusion is strengthened by the observation of a small amount of allyl anion when I1 is allowed to react with a large excess of propylene (AHoacid = 391 kcal/mol).I2 If we postulate AHoacid = 390 f 2 kcal/mol for the acyl hydrogen i n acetaldehyde, the electron affinity of the acetyl radical CH,C=O can be calculated to be 0.42 (hO.10) eV (10 kcal/mol), and indeed a small amount of 02-is formed when an excess of O2(EA = 0.44 eV)I3 reacts with II.I4 These conclusions are strongly supported by preliminary photodetachment data of Nimlos et al.,I5 which give EA(CH3C=O) = 0.438 (f0.020) eV. The acetyl anion is highly reactive and atom transfer is observed with N20,16COS,’7 and CS2.I8 The main products of its reaction with oxygenI9 also involve atom transfer.20 CH,C=O
+
N,O
-
CH,CO,-
-t
N,
(3)
CH,&O
+
COS
-
CIi,COS-
4-
CO
(4)
CH,C=O
+
CS2
-
CH,COS-
CS
(5)
+
0
(6)
CH,E=O
0,
HO
(7)
%? CH,C02CH,CO,-
+ + +
(11) The (M - 1) ion from I is a minor product (
