Cyclopentene and methylcyclopentene ions were generated by irradiating the respective parent compounds with 10.0‐eV photons; cyclopentene was also irradiated with 11.6–11.8‐eV photons. The ionic products of ion–molecule reactions were observed in the NBS high‐pressure photoionization mass spectrometer, while the neutral products of these reactions were determined by chemical analysis of products formed in photolytic experiments in a closed system. The cyclopentene ion, which at 10.0 eV retains its cyclic structure, undergoes an H2 transfer reaction (c‐C5H8++c‐C6H8c‐C5H10+c‐C5H6+, k = 3.3 × 10−10cm3/molecule·sec) and a condensation reaction (c‐C5H8++c‐C5H8→C10H16, k = 2.7 × 10−10cm3/molecule·sec) with the parent molecule. The same reactions are observed for ions formed at 11.6–11.8 eV, but at the higher energy, approximately 20% of the ions are observed to undergo ring opening to form 1,3‐C5H8+ ions; the latter ions undergo an H2 transfer reaction with the cyclopentene molecule (1,3‐C5H8++c‐C5H8→2‐C5H10+C5H6+, k = 1 × 10−10cm3/molecule·sec). The three methylcyclopentene ions also undergo H2 transfer reactions with the corresponding parent molecules [C6H10++C6H10→(CH3)C5H9+C6H8+, k = 4.6, 1.8, and 2.9 × 10−10cm3/molecule·sec for 1‐, 3‐, and 4‐methylcyclopentene, respectively]. Condensation reactions between these ions and their parent molecules are observed to only a minor extent, but a second major mode of reaction, namely H transfer, is observed (C6H10++C6H10→C6H11+C6H9+, k = 0.6, 2.8, and 1.2 × 10−10cm3/molecule·sec for 1‐, 3‐, and 4‐methylcyclopentene, respectively). Structural reasons for these rate variations are discussed.

1.
R. Lesclaux, S. Searles, L. W. Sieck, and P. Ausloos, J. Chem. Phys. (to be published).
2.
(a) J. H. Futrell and T. O. Tiernan, in Fundamental Processes in Radiation Chemistry, edited by P. Ausloos (Interscience, New York, 1968), p. 171.
(b) Ion‐Molecule Reactions, edited by J. Franklin (Plenum, New York, 1971).
3.
R.
Gorden
, Jr.
,
R. E.
Rebbert
, and
P.
Ausloos
,
Natl. Bur. Std. (U.S.), Tech. Note
496
, (
1969
).
4.
L. W.
Sieck
,
S. K.
Searles
, and
P.
Ausloos
,
J. Am. Chem. Soc.
91
,
7627
(
1969
).
5.
P.
Ausloos
and
S. G.
Lias
,
Radiation Res. Rev.
1
,
75
(
1968
).
6.
S. K.
Gupta
,
E. G.
Jones
,
A. G.
Harrison
, and
J. J.
Myher
,
Can. J. Chem.
45
,
3107
(
1967
).
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