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Unformatted text preview: n carboxylic acid because it has higher pKa therefore it is less acidic and it is
harder to remove the hydrogen therefore it is a stronger bond causing more vibration
s, m, v: tell you about intensity
s: Strong m:Medium v:Variable 4 IR – Identify the key absorptions: Comple Stretch and
compress medium Carbonyl carbonyl Hard to
<1500 Absorba Transmit W
nt IR – Identify the key absorptions: broad
stretch sp3 C-H 1bu
no OH 6 IR – Identify the key absorptions: 1 degree= 2 degree=1 NH2
mi 7 IR – Identify the key absorptions: 3000-33 8
to IR – terminal alkyne 9 5- Nuclear magnetic resonance (NMR)
• Use to precisely identify the structure of
O vs O In CHM 2120, we will analyze protons
(1H) only. Other nuclei (2H, 12C, etc) are
“invisible” to the spectrometer in a 1H
NMR experiment. 10 PROTON (1H) NMR
A typical spectrum: H3C 4 3 H2
O O CH3 2
PPM 1 0 Key characteristics of a spectrum (4) Chemical Shift (δ) Chemical equivalence/non-equivalence Integration of signal area Multiplicity (also called coupling or splitting) 11 Chemical Shift (δ)
• Position of signal along X-axis (measured in ppm)
• The chemical shift gives indication of structural
environment of the nucleus (i.e. proton)
• A proton with high electron density is termed
shielded (or surrounded, by electron density).
• A proton with low electron density is termed
deshielded (electron density is pulled away from
12 What factors affect the chemical shift?...
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This document was uploaded on 03/17/2014 for the course CHM 2120 at University of Ottawa.
- Spring '10