1) Of homotopic, enantiotopic, and diastereotopic hydrogens, which one(s) have the same chemical shift and which ones(s) have different chemical shifts? Locate the three types of protons in 1- and 2-bromobutane.   2) Draw a 1H NMR spectrum of 1-bromobutane having the chemical shifts in the correct order.   3) Predict the number of signals in the decoupled 13C NMR spectrum of all the structural isomers of C5H11Br.

A spectrum recorded during the infancy of NMR. http://www.nmr.varian.com/

4) Compound A (C4H8O2) has the 1H NMR spectrum shown below. When compound A reacts with an

excess of CH3MgBr, two compounds, B and C, are isolated. The 1H NMR spectrum of B is shown on

the right in an old spectrum. One of the signals in this spectrum disappears when D2O is added to the

sample. Compound C has only two singlets (9:1 ratio) in its 1H NMR spectrum. The smaller singlet

disappears on addition of D2O to the sample. What are the structures of A-C? Explain. [The signals in

the spectrum (reading from left to right) are a quartet, singlet, and triplet.]

5) Compound A (C6H12O) reacts with NaBH4 to form B (C6H14O). Treatment of B with H2SO4 at 150 oC

provides C (C6H12). Exposure of C to OsO4 (catalytic) and H2O2 affords D (C6H14O2). The reaction of

D with H2SO4 at 100 oC gives A. Compound A: 1H NMR d 2.2 (3H, s) and 1.1 (9H, s). [The chemical

shifts are estimated.] What are the structures of A-D? Explain. [Notice that there is a two electron

reduction and a two electron oxidation in the cycle of A --> B --> C --> D --> A.]

6) During free radical chlorination of A (C5H12) a dichloro compound B was isolated. The 1H NMR

spectrum of B displayed two singlets in a 3:2 ratio while the decoupled 13C NMR spectrum displayed

three singlets, one of which was a weak signal. What are the structures involved? Explain.

7) Predict the number of singlets in the proton decoupled 13C NMR spectrum of the following alkyl halides.

Illustrate.

8) Estimate the frequency (MHz) of the 1H NMR spectrometer that recorded the spectrum shown to the right

of problems 1 -3. The chemical shifts are d 1.11 for the triplet and d 3.56 for the quartet. Assume the

value of J = 7.0 Hz. A blow-up of the necessary part of the spectrum is shown below.