O2: 32 Structure determination

Question 1

How can structures of new compounds be confirmed?

In general

Answer 1

By a range of analytical techniques, developed by scientists.

Question 2

What does NMR give information about?

Answer 2

The position of 13C or 1H atoms in a molecule.

Question 3

Between 13C NMR and 1H NMR, which one gives simpler spectra?

Answer 3

13C NMR

Question 4

What does chemical shift depend on?

Answer 4

The molecular environment.

Question 5

What do integrated spectra indicate?

Answer 5

The relative numbers of 1H atoms in different environments.

Question 6

How are 1H NMR spectra obtained?

What solvent is used to dissolve samples?

Answer 6

Using samples dissolved in CCl4.

Question 7

What is used as a standard in NMR?

Answer 7

Tetramethylsilane (TMS).

Si(CH3)4

Question 8

Why is tetramethylsilane a suitable substance to use as a standard?

Answer 8

• produces a single absorption peak
• peak is away from other absorption peaks
• inert
• non-toxic
• volatile, so easy to remove (low bp)