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preface to fifteenth edition

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SPECTROSCOPY 7.47<br />

TABLE 7.20<br />

Absorption Frequencies of Single Bonds <strong>to</strong> Hydrogen (Continued)<br />

Group Band, cm 1 Remarks<br />

Miscellaneous R9H<br />

9S9H 2600–2550 (w) Weaker than OH and less affected by H<br />

bonding<br />

P9H 2440–2350 (m) Sharp<br />

O<br />

P<br />

2700–2560 (m) Associated OH<br />

OH<br />

R9D<br />

100/137 times the<br />

corresponding RH<br />

frequency<br />

Useful when assigning RH bands; deuteration<br />

leads <strong>to</strong> a known shift <strong>to</strong> lower frequency<br />

TABLE 7.21<br />

Absorption Frequencies of Triple Bonds<br />

m, moderately strong<br />

m–s, moderate <strong>to</strong> strong<br />

s, strong<br />

Abbreviations Used in the Table<br />

var, of variable strength<br />

w–m, weak <strong>to</strong> moderately strong<br />

Group Band, cm 1 Remarks<br />

Alkynes<br />

Terminal 3300 (s) CH stretching<br />

2140–2100 (w–m)* C#C stretching<br />

1375–1225 (w–m)<br />

695–575 (m–s) Two bands if molecule has axial<br />

symmetry<br />

ca 630 (s) Alkyl monosubstituted<br />

Nonterminal 2260–2150 (var)* Symmetrical or nearly symmetrical substitution<br />

makes the C#C stretching<br />

frequency inactive. When more than<br />

one C#C linkage is present, and<br />

sometimes when there is only one,<br />

there are frequently more absorption<br />

bands in this region than there are<br />

triple bonds <strong>to</strong> account for them.<br />

R 1 9C#C9R 2 540–465 (m) The longer the chain, the lower the frequency<br />

Aryl9C#C9<br />

9C#C9halogen (Cl, Br, I)<br />

ca 550 (m)<br />

ca 350 (var)<br />

185–160 (var)<br />

* Conjugation with olefinic or acetylenic groups lowers the frequency and raises the intensity. Conjugation with carbonyl<br />

groups usually has little effect on the position of absorption.

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