Instant Notes: Analytical Chemistry

A consequence of the small difference between the energy levels is that their populations are almost equal at room temperature. ...

All nuclei are assigned a spin quantum number, I, on the basis of the number of protons and neutrons in the nucleus, the values ...

electrons, and this determines the value of s, and hence n. The exact position of each resonance frequency is referred to as its ...

identical protons or the four identical carbon-13 nuclei. The protons and the carbons are all highly shielded due to the relativ ...

254 Section E – Spectrometric techniques Table 4. Variation of the chemical shift of methylene protons with distance (number of ...

● The illustrations show that alkene (~5.3 d/ppm) and aromatic protons (~7.3 d/ppm), and those close to a carbonyl double bond ( ...

The spins of neighboring groups of nuclei in a molecule are said to be coupledif their spin states mutuallyinteract. The interac ...

described as first orderwhen the numbers of components and their relative intensities are as predicted by the n+ 1 rule and Pasc ...

258 Section E – Spectrometric techniques nA dA nX nA dX nX dA dX JAX JAX JAXJAX JAX Orientations of X spin A spin Area ratio 1:1 ...

spectrum mathematically in less than a second by a computer using a fast Fourier transform(FFT) algorithm. Multiple interferogra ...

Stability of operation is improved considerably by lockingthe field and frequency together to correct for drift. This is achieve ...

Section E – Spectrometric techniques E13 NUCLEAR MAGNETIC RESONANCE SPECTROMETRY: INTERPRETATION OF PROTON AND CARBON-13 SPECTRA ...

series of steps, generally displayed above each resonance signal. The vertical height of each step, in arbitrary units, gives th ...

● Note the presence or absence of saturated structures, most of which give resonances between 0 and 5 d/ppm (trichloromethane at ...

The CH(methine) resonance in 1,1,2-trichloethane(Fig. 4) is at a much lower field than the CH 2 (methylene) resonance because of ...

E13 – NMRS: interpretation of proton and carbon-13 spectra 265 Cl OCH CH 3 COOH 11 10 9 8 7 6 d (ppm) 543210 1 4 1 3 600 500 400 ...

The CH 2 protons in propanamide(Fig. 7) are deshielded by the adjacent carbonyl group and couple with the CH 3 protons to give a ...

The two CH 3 groups in isopropyl benzene(Fig. 8) are identical and their resonance is split into a doublet by the adjacent CH, w ...

268 Section E – Spectrometric techniques d (ppm) 190180170160150140130120110100 90 80 70 60 50 40 30 20 10 0 H 3 C H 3 C CH CH C ...

Apart from the CH 3 carbon at 22 d/ppm, the remaining carbon-13 resonances in 3-hydroxy methylbenzene(Fig. 11) are all in the un ...