Chapter 32 (Structure Determination)

Question 1

What factors influence choice of pathway?

Answer 1

• Availability/cost of starting materials
• Number of stages needed to convert target molecule
• If more than one product formed/purification needed
• Number and cost of separation
• Percentage yield expected
• Atom economy of overall process
• Amount of waste generated
• If toxic chemicals needed

Question 2

Why is TMS used to calibrate spectra?

Answer 2

• Gives one signal
• Non-toxic and inert
• Has low boiling point
• Gives signal that is far to the right of signals of organic compounds

Question 3

What is shown on a Proton NMR?

Answer 3

• Number of signals: How many different sets of equivalent H atoms there are
• Positions of the signals: Suggests environment that H atom is found
• Relative intensity: How many H atoms are found in that environment

Question 4

What affects the chemical shift of the absorbance in H NMR?

Answer 4

• The closer the H is to electronegative atoms, the greater the shift
• The more electronegative atoms the greater the shift

Question 5

What does splitting in H NMR show?

Answer 5

Provides information about the number of H atoms on the adjacent carbon.

singlet = no H on next carbon

doublet = 1 H on next carbon

triplet = 2 H on next carbon

quartet = 3 H on next carbon

Question 6

How is absorbance strength found for H NMR?

Answer 6

Area under each peak