ORG CHEM 3 Flashcards
Benzyne is a very reactive intermediate. As a result, it is very difficult to track chemical reactions. How was its existence demonstrated?
By trapping the intermediate in a cycloaddition reaction
By separating it from the mixture by GC/MS
By separating it from the mixture by column
chromatography
None of the above
By trapping the intermediate in a cycloaddition reaction
Benzyne is the mechanistic intermediate for which of the following reactions?
Nucleophilic additions
Electrophilic additions
Cycloadditions
All of the above
All of the above
Chain reactions involving free-radicals occur in which of the following orders?
Initiation, propagation, termination
Initiation, termination, propagation
Propagation, termination, initiation
Termination, propagation, initiation
Initiation, propagation, termination
Given that the energy of a CH3-H bond is 104 kcal/mol and that of an HO-H bond is 119 kcal/mol, what is the bond dissociation energy of the following reaction?
15 kcal/mol
-15 kcal/mol
223 kcal/mol
-223 kcal/mol
-15 kcal/mol
Given that the energy of a CH3bond is 104 kcal/mol, CH3-Cl bond is 85 kcal/mol, H-Cl bond is 103 kcal/mol and that of an Cl2 bond is 58 kcal/mol, what is the bond dissociation energy of the following reaction?
25 kcal/mol
-25 kcal/mol
189 kcal/mol
-166 kcal/mol
-25 kcal/mol
Identify the most stable free radical.
I
II
III
IV
II
Nitrogen ylides are very versatile and can be used in a number of chemical reactions. Which of the following is a reaction of nitrogen ylides?
Cannizzaro reaction
Sommelet reaction
Blanc reaction
Friedel-Crafts reaction
Sommelet reaction
Nitrogen ylides are very versatile and can be used in a number of chemical reactions. Which of the following reactions is NOT a reaction of nitrogen ylides?
Stevens reaction
Sommelet reaction
Wittig reaction
Friedel-Crafts reaction
Friedel-Crafts reaction
What are common methods for preparing benzyne?
Elimination from organolithium or organomagnesium precursors
loss of neutral leaving group
photolytic and/or pyrolitic methods
All of the above
All of the above
What is the major product of the radical reaction of 2-methylbutane with Cl2?
2-chloro-2-methylbutane
1-chloro-2-methylbutane
3-chloro-2-methylbutane
4-chloro-2-methylbutane
2-chloro-2-methylbutane
Which of the following is NOT a method for generating free radicals?
Thermal cracking
Photolysis bond heterolysis
Homolysis of peroxides and azo compounds
Electron transfer
Photolysis bond heterolysis
Which statement about free radicals is incorrect?
Free radicals contain an unpaired electron.
Radicals are believed to be involved in degenerative diseases and cancers.
They are formed by heterolytic cleavage of bonds.
Radicals can either be neutral or ionic.
They are formed by heterolytic cleavage of bonds.
chloro-3-methylhexane undergoes SN2 reaction with sodium ethoxide. This reaction yields low amount of products. However, addition of small amounts of sodium iodide increases the rate of the reaction. Why?
The charge of the sodium ion stabilizes the charge of the chloride ion.
The iodide ion renders the ethoxide ion more reactive.
Small amounts of alkyl chlorides are converted into the more reactive alkyl iodides.
With the presence of NaI, the mechanism changes to SN1.
Small amounts of alkyl chlorides are converted into the more reactive alkyl iodides.
Which of the following compounds will be the most reactive substrate in SN1 reactions?
(C2H5)3CCl
(C2H5)2CHCl
C2H5CH2Cl
(C2H5)3CF
(C2H5)3CCl
Which of the following statements about chirality is incorrect?
A chiral center is an atom that is tetrahedrally bonded to four different groups.
A chiral molecule has a superimposable mirror image.
A chiral molecule does not have any reflective symmetry.
All chiral molecules may exist as enantiomers.
A chiral molecule has a superimposable mirror image.
Which of the following statements best describes an E2 reaction?
It involves a two-step mechanism.
It involves a very reactive intermediate.
The rate of the reaction depends on the concentration of the base.
The rate of the reaction increases in polar solvents.
The rate of the reaction depends on the concentration of the base.
The Grignard reaction is an important reaction to provide which of the following?
Carbon-carbon bonds
Carbon-magnesium bonds
Carbon-halide bonds
Magnesium-halide bonds
Carbon-carbon bonds
What happens to the chiral center when (R)-3-methyl-3-phenyl-4-heptanone reacts with phenylmagnesium bromide?
Inversion of configuration occurs.
A racemic mixture is formed.
Nothing, the chiral center remains unchanged.
The product is achiral.
Nothing, the chiral center remains unchanged.
What is organometallic chemistry?
The study of carbon containing compounds
The study of compounds containing a carbon-metal bond
The study of metals
The study of salts
The study of compounds containing a carbon-metal bond
Which of the following reactions would be a useful way of preparing 1-phenyl-1-butanol?
Butanal and phenylmagnesium bromide
1-phenyl-3-butanone and NaBH4
Propanal and benzylmagnesium bromide
Both A and C
Butanal and phenylmagnesium bromide
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