Carboxylic acid because it has higher pka therefore

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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 interpret Ignore <1500 Absorba Transmit W av en u m be rs = fre qu CH Str et ch M et hyl Bu ta no at 5 Ea ch co m po un d ha s a "fi ng er pri nt IR – Identify the key absorptions: broad peak stretch sp3 C-H 1bu ta no OH 6 IR – Identify the key absorptions: 1 degree= 2 degree=1 NH2 1bu tyl a mi 7 IR – Identify the key absorptions: 3000-33 8 be nz yl iso pr op yl ke to IR – terminal alkyne 9 5- Nuclear magnetic resonance (NMR) • Use to precisely identify the structure of unknown compounds 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 C C 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 the proton). 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.

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