Diee the peak matching tor the problem on Spec Extra 10, p. 5 B. Nuclear Magneti

Question

Diee the peak matching tor the problem on Spec Extra 10, p. 5 B. Nuclear Magnetic Resonance (c NMR) 1. Differences from 'H NMR 2. Chemically-distinct Carbons 3. Most important things to remember about 13c NMR (and role of symmetry) 4. Evaluate: Spec Extra # 3 & 4, pp.48-use an NMR Table to facilitate the analysis C. Infrared Spectroscopy 1. Intro: what is it and why do we use it? 2. IR Chart: Note landmark absorptions (O-H, C-H, ?-?, ?-?, C-O, etc) 3. IR spectra of 2-hexanol and 2-hexanon 4. Spec Extra #11, Problem 2:What are the most significant peaks in each structure? 5. Examine the IR spectra of camphor and isoborneol that are at the end of the Ro experiment. While they are similar, they also have differences. What are those differences e- compare the peaks present and absent in each spectrumm s?

Explanation / Answer

The 13C NMR is generated in the same fundamental as of H1 NMR spectrum. Only 1.1 % of naturally occurring carbon is C- 13 and actually an advantage because of less coupling.

Requirement for NMR:

Spin quantum number (I)?0.

The C-13 NMR is directlyabout the carbon skeleton not just the proton attached to it.

The number of signals tell us how many different carbons or set of equivalent carbons. The splitting of a signal tells us how many hydrogens are attached to each carbon. (N+1 rule)hence the chemical shift tells us the hybridization (sp3, sp2, sp) of each carbon.

IR

1.IR Spectroscopy measures the vibrations of atoms, and based on this it is possible to determine the functional groups. Generally, stronger bonds and light atoms will vibrate at a high stretching frequency (wavenumber) and the wavenumber is plotted against the % transmittance.

2. O-H 3500 cm-1

1650 cm-1 C=O

1675cm-1    C=C

1210cm-1    C-O

3. In the 2-hexanone the predominant peak is the peak corresponding to the ketone near the 1615 cm-1. 2-Hexanol gives the broad spectra of OH stretching nearby the 3500cm-1 mark.

5. camphor and isoborneol also can be differentiated owing to the broad OH stretching corresponding to the OH isoborneol while camphor has sharp peak corresponding to the carbonyl stretching.

333-3267cm-1 C-H stretching alkyne 3100-3000cm-1 C-H stretching alkene 3000-2840cm-1 C-H stretching alkane

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