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Unformatted text preview: 14-8 Calculate the Amax for each of the following compounds. CHZCHZCH3 CH2CH3 CH CH3 3 OH
i HO : HZN. :
CH3 CH3 CH3 14-9 Calculate Amax for the following steroids.a
(a) \\ \ \\ 275 r '~ Observed
Amax (nm) 239 235
Emax 17,300 19,000 10,000 t (b) ‘ \ \ \ g
EtO AcO ' MeS
Amax (nm) 268 241 235
gm, 22,600 22,600 19,000 1 1 D I AcO
AW (nm) 283 285 355
smax 33,000 9,100 19,700
(d) 0: g O : :
Amax (nm) 230 241 254
Emax 10,000 16,600 9100
[email protected] 1131 l
Amax (nm) 244 290 292
emax 15,000 12,600 13,000 aObserved data from A. 1. Scott, Interpretation of the Ultraviolet Spectra of Natural Products, New York: Pergamon Press, 1964, 442 Part IV 0 Electronic Absorption Spectroscopy (f) E :
: i: ;o O 0 Observed ’
348 327 Amax (nm) 348
1 1 ,000 26,500 5 max 14-10 Calculate the 77' -> 77* transition Amax for cholesta—4,6-diene-3-one (a) and its enol acetate (b).
CSH17 C8H17 (b) /©§j
ACO 14-11 What UV—vis Amax would you predict for the 71' —> 77* transitions of the following com— pounds?
0 14-12 Calculate the approximate Amax for the 7r —+ 7* transition of each of the following com- pounds.
M 0* 14-13 Calculate the approximate Amax for the 71 —+ 77* transitions of each of the following com— pounds.
0 : : ; : o“ O , 14-14 An enol acetate of cholest—4-ene-3-one (a) is prepared and has Amax = 238nm with
log Emax = 4.2. Is the enol acetate b or c? a? 03 ed
0 AcO AcO .
(a) (b) (c) 14-15 Spiroenones (a) and (b) were prepared. One showed an intense Amax at 247 nm, the other at
241 nm. Assign the structures. (a) V (b) (a)
O Chapter 14 0 Structural Analysis 443 14-16 Predict and explain whether UV—Vis spectroscopy can be used for distinguishing members
of the following isomeric pairs. (a)
o o (b) , . i
' and a O O . p ‘ (C) CH OH OH and CHZCH3 ' (d) (I) 0 l H
QC—CHZCH3 and CHZC—CH3 (e) CH3CH2COOCH3 and CH3COOCH2CH3
and CH3CH2—CH=CH—CH=CH—-CH3 14-177 A compound (A), C11H16, has Amax 288 nm. On treatment with Pd / C (which dehydro-
genates cyclic compounds completely to aromatic compounds without rearrangement),
a—methylnaphthalene (below) is produced. What is the structure of A? 14-18 An unknown monocyclic hydrocarbon A, C8H14, has a Amax at 234 nm and could be selec-
tively ozonized to yield B, C7H120, which has Amax at exactly 239 nm. Reduction of B with
LiAlH4 and careful elimination of water (dehydration) gave C, C7H12, which has a Amax at
267 nm. Give structures for A, B, and C. 14-19 Explain the following observations. 0 O
/ _ /
\ \ OL-IOIIOIIC B—Ionone lP-Ionone Observed
Amax (nm) 228 ‘ 281 291
smax 14,300 9500 21,800 14-20 An unsaturated ketone, CngZO, was thought to have the structure given below. Its UV
spectrum showed Amax 300 nm with A = 1.34. O (a) Is the suggested structure correct? Apply the Woodward-Fieser rules. (b) Write a structure that satisfies the Amax and has the same carbon skeleton. (c) Determine the molecular extinction coefficient 6 for the recorded spectrum determined
in a 1 cm cell with 4 mg of compound in 200 ml of solvent. ...
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- Fall '11