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Various Organic Chemistry Questions

I am taking an entrance exam for graduate school next month and I've been out of school for over a year now and I really need help and indepth explanations on how to do these problems from the online practice test. I am also using review notes from class and notecards to help me, but I want more help on an actual practice exam.
I will post the questions as well as the website from which they came from.
Here it is:

71. In the reaction energy diagram shown below,
what is the intermediate species?
A. A
B. B
C. C
D. D
E. E

72. A characteristic feature of the SN2 reaction
mechanism is that
A. it follows first-order kinetics.
B. it produces stereochemical inversion of
C. there is no rate-determining step.
D. steric factors have little influence on the
reaction rate constant.
E. collision of three or more particles is

73. It is believed that an unlabeled bottle
containing an unknown liquid is either 2-
pentanone or 3-pentanone. What is the best
methodology to distinguish one compound
from the other?
A. Mass Spectroscopy
B. Infrared Spectroscopy
C. 13C NMR Spectroscopy
D. Thin Layer Chromatography
E. Melting Point Determination

74. What is the produce of the following reaction

75. Which statement is true regarding a
compound that has multiple chiral centers and
a plane of symmetry?
A. It is chiral.
B. It is assymetric.
C. It is an enantiomer.
D. It is meso.
E. It rotates plan polarized light.

76. Nitration of toluene (Phâ?"CH3) with
HNO3/H2SO4 occurs
A. faster than nitration of benzene and
produces mostly ortho and para
B. slower than nitration of benzene and
produces mostly meta product.
C. faster than nitration of benzene and
produces mostly meta product.
D. slower than nitration of benzene and
produces mostly ortho and para
E. at the same rate as nitration of benzene
and produces mostly meta product.
77. Which of the following carbocations is the
most stable?

78. Which of the following does a strong infrared
absorption band between 1750 and
1700 cmâ?"1 (5.77 - 5.88m ) indicate the
presence of?

79. According to IUPAC rules, which functional
group is given the highest priority when
numbering the parent chain?
A. Amines
B. Alkenes
C. Aldehydes
D. Amides
E. Acid Anhydrides

80. Which of the compounds below would be
most soluble in water?

81. Which of the conformations of
1,3-dimethylcyclohexane is the least stable?
82. Which ONE of the following pure liquids
would be expected to show extensive
intermolecular hydrogen bonding?

83. Which of the following compounds is a tertiary
(3° ) amine?

84. Which of the following compounds best fits
the 1H NMR spectral data listed below?

85. Which of the following will undergo a free
radical bromination most rapidly?

86. How many Ï? molecular orbitals does pyridine
A. 3
B. 4
C. 5
D. 6
E. 7
87. Which combination of reagents will produce

88. Which of the following statements is true
regarding a pair of compounds that are
diasteromers of each other?
A. They are configurational isomers.
B. They have the same physical
C. They are mirror images.
D. They are always optically active.
E. They have equal but oppisite ? values.

89. The indicated H atom on imidazole is acidic.
This can best be explained by stabilization of
the conjugate base. Which of the following is
the greatest cause of this stabilization?
A. The inductive effect
B. Resonance
C. Conjugation
D. Aromaticity
E. Hyperconjugation

90. What is the product of the following sequence
of reactions?

91. Which reagent, followed by the appropriate
work-up procedure, could you use to effect
the following conversion?
92. What is the product of the following addition

93. What is the hybridization of a nitrogen atom if
it forms two Ï? two Ï? bonds?
A. sp
B. sp2
C. sp3
D. sp3d2

94. Which of the following is a group that is both
deactivating and ortho, para directing in the
nitration reaction of substituted benzenes?
B. CH3
C. Br
D. NO2

95. Which of the following functional groups can
act as both a BrÃ?nsted acid and BrÃ?nsted

96. What is the major product of the following
97. Which of the following ions is stabilized by

98. Treatment of benzoic acid with thionyl
chloride followed by addition of ethanol gives
which of the following as the major product?

99. What is the major product (B) of the following
reaction sequence?

100. The most acidic hydrogen(s) in the following
compounds are attached to which of the
following carbons?
A. 1
B. 2
C. 3
D. 4
E. 5.

Solution Preview

These are my views:

C is the intermediate - this is in an energy trough - it has a relative stability compared to B and D
B and D are transition states - these are at the peaks in energy (i.e. they are not stable!)
A is the starting material
E is the product
B is correct.
If you look at the mechanism, a nucleophile attacks, in terms of projector, from behind the leaving group. This causes the overall stereochemistry to switch!
I would go for A, mass spec. The others would all give inconclusive and similar results for both compounds. In mass spec, the molecular ion would be the same, but any fragmentation would be unique!
The product is A. Deprotonation between the esters generates an anion that is alkylated. The acid then decarboxylates and hydrolyses the remaining ester to a carboxylic acid.
A meso compound has chiral centres and a plane of ...

Solution Summary

The solution assists with answering and explaining various organic chemistry questions.