Ch17 Spectroscopy

Question 1

What are the different types of covalent bond vibrations in IR spec and what does the frequency of vibration depend on?

Answer 1

Question 2

What is the fingerprint region on IR graph? Where can functional groups be identified?

Question 2

What is the fingerprint region on IR graph? Where can functional groups be identified?

Answer 2

• Fingerprint region = below 1500cm-1 wavenumber ; unique peaks that can be used to identify molecule by comparison w/ spectra of known compounds. Can help distinguish if compound contains impurities if compared to known spectra of pure compound.
• Above 1500cm-1 peaks are useful to identify functional groups present in molecule.

Question 3

LOOK AT IR SHEET on IPAD

Answer 3

Question 4

What is a molecular ion on Mass Spec:

Answer 4

The molecular ion peak is the peak at highest m/z value on RHS of mass spec
Might be a very small peak one unit after M+ peak, known as M+1 due to small % of carbon present at carbon-13 isotope rather than carbon-12.

Question 5

What is fragmentation on a mass spec:

Answer 5

• Inside mass spec, some of molecular ions undergo fragmentation, where they break down into smaller fragments (covalent bonds break).
• The fragment ions produce other peaks seen in mass spec
• When M+ breaks down it produces both positively charged fragment ions and radicals, but only positive ions can be detected (not uncharged radicals)

Question 6

LOOK THROUGH MASS SPEC SHEET ON IPAD