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The rate of the gas phase reaction of hydroxyl radical with methyl nitrate has been measured to be (3.4 * 0.4) x cm3 molecule-' s-' at 298 K using flow discharge/ resonance fluorescence techniques. By means of correlation methods, this rate determination is used to predict a vertical ionization potential of 12.6 eV, a bond dissociation energy for H-CH20N02 of 101 kcal mol-', and a rate for O?P) reaction with methyl nitrate of ca. 9 x cm3 molecule-' s-'. In conjunction with previously derived relative data for reaction of alkyl nitrates with OH radical in the gas phase, a priori estimated reactivities for 1-, 2-, and 3-positionally substituted straight chain alkyl nitrates have been reexamined. Revised reactivities for OH abstraction of specific hydrogens substituted on straight chain alkyl nitrates are presented and discussed, and an atmospheric lifetime of ca. 2 yrs is estimated for methyl nitrate removal due to OH.

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Sir: The measurement of peroxycarboxylic nitric anhydrides (so-called PAN-type compounds) has become a crucial part of atmospheric chemical research. One such compound, peroxyacetic nitric anhydride (PAN), has been shown to comprise a large fraction of photochemically active nitrogen (1,2), which is often referred to as reactive odd-nitrogen (NCy. PAN, while originally discovered and measured by IR spectroscopy (3,4), is routinely measured by gas chromatography with electron capture detection (GC/ECD) (5). The packed columns used for this analysis have changed little in the past 25 years and have consisted mainly of low-molecular-weight Carbowax liquid phases on deactivated solid supports. Alkyl nitrates (R0N02) have emerged as another class of compounds