PARAMAGNETIC RESONANCE OF LIQUID SULFUR - DETERMINATION OF MOLECULAR PROPERTIES
PARAMAGNETIC RESONANCE OF LIQUID SULFUR - DETERMINATION OF MOLECULAR PROPERTIES
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DOI：
10.1021/ja01595a011
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发表时间：
1956-01-01
影响因子：
15
通讯作者：
FRAENKEL, GK
中科院分区：
文献类型：
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作者：
GARDNER, DM;FRAENKEL, GK
在189-414℃下，从液态硫中获得了顺磁共振波谱。顺磁性随温度可逆地增大，直接证实了长链硫聚合物的存在，所得结果与GEE的理论预言是一致的，即长链与SS环之间存在平衡。长链中硫-硫键的断裂热为33。4±4.8千卡/摩尔。在300℃时，自由基浓度为(1.1±0.6)×10~(-3)摩尔/l，平均链长在171℃时达到最大值(1.5±0.7)×10~(6)。这些值与由热容数据解释得到的估计值之间有很好的一致性。共振线宽随温度的升高而显著增大，但光谱分裂因子(g值)与温度无关。线宽的行为被解释为快速自由基置换反应的证据，给出了速率常数k=2.8×108exp(-3100/RT)1.(g.原子)-1秒-1。通过加热普通纯度的硫磺得到的黑色斑点也观察到了顺磁共振光谱。本文介绍了高温顺磁共振波谱技术以及获得绝对和相对顺磁强度的方法。
Paramagnetic resonance spectra have been obtained from liquid sulfur at temperatures from 189 to414. The para-magnetism, which increases reversibly with temperature, provides direct confirmation for the existence of long-chain sulfur polymers, and the results obtained are in quantitative agreement with the predictions of thetheory due to Gee that postu-lates an equilibrium between long chains and Ss rings. The heat of scission of sulfur-sulfur bonds in a long chain was found to be33. 4±4.8 kcal./mole. The concentration of radicals at 300 was found to be (1.1±0.6) X 10-3 mole/1. and the average chain length is estimated to reach a maximum value of (1.5±0.7) X 106 at 171. Good agreement exists between these values and the estimates obtainedfrom interpretation of the heat capacity data. The line width of the resonance increases markedly with temperature, but the spectroscopic splitting factor (g-value) is independent of temperature. The behavior of the line width is interpreted as evidence for a rapid radical displacement reaction giving for the rate constant k= 2.8 X 108 exp (—3100/RT) 1.(g.-atom)-1 sec.-1. Paramagnetic resonance spectra have also been observed from the black specks obtained by heating sulfur of ordinary purity. A description is given of the techniques of high temperature paramagnetic resonance spectroscopy and of the methods of obtaining absolute and relative paramagnetic intensities.