Exam 11: Structure Determination: Nuclear Magnetic Resonance Spectroscopy

Instructions: Predict the splitting patterns you would expect for each proton in the molecules below: Predict:

Which of the following combinations of peaks appears in the ¹H NMR spectrum of 2-methylpropane?

Which of the following combinations of peaks appears in the ¹H NMR spectrum of diethyl ether,CH₃CH₂OCH₂CH₃?

How many positive and negative peaks appear in the DEPT-135 and in the DEPT-90 spectrum of 2-methylpentane?

Which of the following compounds gives a ¹H NMR spectrum consisting of only two singlets?

Instructions: For each of the compounds below tell how many signals you would expect the molecule to have in its normal,broadband decoupled ¹³C NMR spectra. -Number of signals:

Which of the following would produce only singlets in an ¹H NMR spectrum?

How many signals appear in the broadband-decoupled ¹³C NMR spectrum of 1,3-dibromobenzene?

Instructions: Predict the splitting patterns you would expect for each proton in the molecules below: Predict:

Instructions: Refer to the structure of 3-methylbutan-2-one below to answer the following question(s). -Refer to instructions.What is the splitting pattern for the hydrogens in 3-methylbutan-2-one labeled A,B,and C,respectively?

Instructions: For each of the compounds below tell how many signals you would expect the molecule to have in its normal,broadband decoupled ¹³C NMR spectra. -Number of signals:

Instructions: For each of the compounds below tell how many signals you would expect the molecule to have in its normal,broadband decoupled ¹³C NMR spectra. -Number of signals:

Nuclear magnetic resonance spectroscopy provides information about a molecule's:

Explain why all protons in a molecule do not absorb rf energy at the same frequency.

A compound with the molecular formula C₅H₁₂O produces only two singlets in the ¹H NMR spectrum. a)Propose a structure for this compound. b)How many signals would be present in the ¹³C NMR for this structure?

Which of the following compounds would produce the most downfield signal in a ¹³C NMR spectrum?

Treatment of tert-butyl alcohol with hydrogen chloride yields a mixture of tert-butyl chloride and 2-methylpropene. a)After chromatographic separation, how would you use ¹H NMR to help you decide which was which? b)How would the ¹³C NMR for the two compounds differ?

Instructions: To answer the following questions,consider the data and ¹H NMR spectrum below. The mass spectrum of this compound shows a molecular ion at m/z = 113,the IR spectrum has characteristic absorptions at 2270 and 1735 cm^-1,and the ¹³C NMR spectrum has five signals. (Spectrum obtained from:SDBSWeb:http://www.aist.go.jp/RIODB/SDBS/) -Refer to instructions.How many types of nonequivalent protons are there in this molecule?

How many sets of equivalent protons are there in hexane,2-methylhexane,and 3-methylhexane,respectively?

If the proton attached to C2 in 1,1,2-tribromopropane is coupled with the protons on C1 (J = 3.5 Hz)and C3 (J = 6.8),draw the tree diagram of the C2 proton and predict the splitting pattern.