Chemistry Reference
In-Depth Information
Learning Objectives
1.
Know the meaning of: NMR, applied magnetic field, spin state, chemical shift,
δ
value, TMS (tetramethylsilane), peak area, spin-spin coupling,
n
+ 1 rule, singlet,
doublet, triplet, quartet, MRI.
2.
Given a structure, tell how many different “kinds” of protons are present.
3.
Given a simple structure, use the data in Table 12.2 to predict the appearance of its
1
H NMR spectrum.
Given a
1
H NMR spectrum and other data such as molecular formula, use Table 12.2
to deduce a possible structure.
4.
5.
Use spin-spin splitting patterns on a spectrum to help assign a structure.
Use
1
H and
13
C NMR spectra with other data or spectra to deduce a structure.
6.
7.
Know the meaning of the functional group region and fingerprint region of an infrared
spectrum, and tell what kind of information can be obtained from each.
8.
Use the infrared stretching frequencies in Table 12.4 to distinguish between different
classes of organic compounds.
9.
In connection with visible-ultraviolet spectroscopy, know the meaning of: nanometer,
electronic transition, Beer's law, molar absorptivity or extinction coefficient.
10.
Know the relationship between conjugation and visible-ultraviolet absorption, and
use this relationship to distinguish between closely related structures.
11.
Know the meaning of: mass spectrum,
m/z
ratio, molecular ion, parent ion,
fragmentation, daughter ion.
12.
Given the molecular formula of a compound, deduce the
m/z
ratio of the parent ion
and predict the relative intensity of the parent + 1 and parent ions.
13.
Given the structure of a simple compound and its mass spectrum, deduce possible
structures for the daughter ions.
14.
Use all spectroscopic methods in conjunction to deduce a structure.
ANSWERS TO PROBLEMS
Problems Within the Chapter
12.1
All of the protons in the structures in part b are equivalent and appear as a sharp,
single peak. One way to test whether protons are equivalent is to replace any one of
them by some group X. If the same product is obtained regardless of which proton is
replaced, then the protons must be equivalent. Try this test with the compounds in
parts a and c. Note that diethyl ether (part a) and propanoyl chloride (part c), has two
sets of equivalent protons (CH
2
and CH
3
).
12.2
a.
CH
3
CH
2
OH 3:2:1
b.
CH
3
CO
2
CH
3
1:1 (or 3:3)
c.
CH
3
CH
2
-O-CH
2
CH
3
2:3 (or 4:6)
12.3
All of the hydrogens in 1,2-dichloroethane are equivalent, and it will show only one
peak in its NMR spectrum. The NMR spectrum of 1,1-dichloroethane will show two
peaks in a 3:1 ratio.
