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606 CHAPTER 17 
 
To see the value of this approach, consider the 
following structure and determine how many 
signals are expected in the 1H NMR and 13C NMR 
spectra of this compound: 
 
H
H3C CH3
H
H3C
H H
CH3
 
 
By redrawing the structure with circles to represent 
aromatic rings (rather than alternating single and 
double bonds), it becomes easier to see that there 
are only two unique kinds of protons in this 
structure (highlighted below): 
 
 
 
This compound will have only two signals in its 1H 
NMR spectrum. 
Similarly, the compound will have only four 
signals in its 13C NMR spectrum: 
 
 
 
Throughout the solutions presented in this chapter, 
we will often represent aromatic rings with circles 
(particularly when symmetry is relevant to the 
discussion). 
 
 
Useful reagents 
The following is a list of reagents encountered in this chapter, as well as their specific function in the context of this 
chapter: 
Reagents Description 
Na2Cr2O7, H2SO4, H2O 
Sodium dichromate and sulfuric acid give chromic acid, which is a strong oxidizing 
agent that can be used to oxidize a benzylic position, provided that the benzylic 
position has at least one benzylic proton. The alkyl group (connected to the aromatic 
ring) is converted into a carboxylic acid group. 
1) KMnO4, H2O, heat 
2) H3O+ 
Potassium permanganate. A strong oxidizing agent that can be used to oxidize a 
benzylic position, provided that the benzylic position has at least one benzylic 
proton. The alkyl group (connected to the aromatic ring) is converted into a 
carboxylic acid group. 
NBS, heat 
N-Bromosuccinimide. A reagent that is used for radical bromination at the benzylic 
position. 
H2O 
Water is a weak nucleophile that can be used in an SN1 reaction with a benzylic 
halide. 
NaOH 
Hydroxide is a strong nucleophile that can be used in an SN2 reaction with a primary 
benzylic halide. 
conc. H2SO4 
A strong acid that can be used to achieve acid-catalyzed dehydration to give an 
alkene. 
NaOEt 
Sodium ethoxide is a strong base that can be used to convert secondary or tertiary 
halides into alkenes (via an E2 process) 
3H2, 100 atm, 150 ºC Conditions for complete hydrogenation of benzene to give cyclohexane. 
Na, CH3OH, NH3 
Reagents for a Birch reduction, which reduces a benzene ring to give a 1,4-
cyclohexadiene ring. 
 
 
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