¹H-NMR spectra for Experiment 4

starting material: 3,3-dimethyl-2-butanone

Monday lab - alcohol product (word or pdf format) (C. Wilcox)

Wednesday lab - alcohol product (word or pdf format) (B. Stokes)

Thursday lab - alcohol product (full spectrum, subspectrum) (B. Adams)

Friday lab - alcohol product (word or pdf format) (T. Pitts)

notes:
(a) turn in with your report the NMR spectra of the starting ketone (above) and the product alcohol (for your lab day)
(b) provide a text summary of the spectra (example below for ethanol)
(c) assign the signals in each spectrum to the H's in the stuctures
(d) comment on product purity and the presence of any other materials in the sample as deduced from the NMR spectrum

you may consult authentic spectra of the cmpds of interest (see sdbs website)

hint: some possible impurities in the product NMR spectrum might be methanol, water, or ether (unlikely). Acetone from cleaning the NMR tube is also an "impurity" sometimes seen in NMR spectra.

Here is an example of the text summary of the ¹H-NMR spectrum of CH₃CH₂OH in CDCl₃ taken on a 90 MHz spectrometer.

ethanol ¹H-NMR (90 MHz,CDCl₃) d(delta)(ppm) 3.69 (q, J=7.3 Hz, 2H), 2.61 (s, 1H), 1.23 (t, J=7.3 Hz, 3H).

s=singlet, d=doublet, t=triplet. q=quartet, m=multiplet, bs=broad singlet.

guidance for NMR analysis:

methanol and water will likely share a common OH peak (because of facile exchange of these H's) which will appear as a broad singlet whose chemical shift may vary (depends on concentation and relative amts of MeOH/water). The methanol methyl singlet may overlap with the methine signal of pinacolyl alcohol - try to pick it out and identify it. Use the sdbs site to find out the chemical shiftvalue expected for the methyl singlet of methanol.

The OH of the product alcohol appears as a separate signal (bs) - it apparently does not exchange fast (i.e. average) with the other impurity OHs due to its steric hinderance.