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1,2,3-Dithiazolyl and 1,2,35-Dithiadiazolyl Radicals as Spin-Bearing ...

1,2,3-Dithiazolyl and 1,2,35-Dithiadiazolyl Radicals as Spin-Bearing ...

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3.3.2 M<strong>as</strong>s Spectrometry<br />

A sample of III-3 w<strong>as</strong> analyzed by EI-MS. The primary function of the m<strong>as</strong>s<br />

spectrum w<strong>as</strong> to identify the presence of the target compound <strong>and</strong> this w<strong>as</strong> successful <strong>as</strong><br />

the parent ion w<strong>as</strong> obtained at m/z = 277 with the positive charge likely being located<br />

primarily on the sulfur atoms. However there w<strong>as</strong> also some fragmentation worth<br />

mentioning. A peak at 2<strong>35</strong> w<strong>as</strong> present indicating the removal of the acetyl group,<br />

although this could be attributed to small amounts of the precursor III-1 contaminating<br />

the sample. The m/z 207 w<strong>as</strong> attributed to the further loss of CO, <strong>and</strong> the other peaks<br />

were difficult to identify b<strong>as</strong>ed on the structure of the sample although may be from<br />

impurities. These are reported in the experimental section at the end of this chapter.<br />

3.3.3 Infrared Spectroscopy<br />

The most effective diagnostic stretching vibrations for III-3 are the peaks <strong>as</strong>sociated<br />

with the carbonyl stretching frequencies.<br />

Figure 3-2 shows the partial infrared<br />

transmission spectra of III-1 <strong>and</strong> III-3. The infrared spectra are only shown from 2000 to<br />

400 cm -1 . The peak at 3280 cm -1 which w<strong>as</strong> present in the starting material which w<strong>as</strong><br />

attributed to the OH stretch w<strong>as</strong> not present in the product III-3. The spectrum for III-3<br />

also h<strong>as</strong> a small peak in this location, but is most likely from a small amount of unreacted<br />

starting material contaminating the sample. The most prominent difference in the IR<br />

spectra from 2000 to 400 cm -1 is the sharp peak at 1758 cm -1 . This peak most likely<br />

arises from the carbonyl of the ester <strong>as</strong> this feature is not present in the spectrum for III-1<br />

<strong>and</strong> is within the range expected for carbonyl stretches of esters b<strong>as</strong>ed on an enol ether<br />

skeleton. The carbonyl stretch from the C=O group attached to the ring system can be<br />

112

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