Ochem Exam 2 material (CH 4-6)
Which of the following molecules is achiral?
(2S,4R)-2,4-Dichloropentane
Which alkyl halide would you expect to react most slowly when heated in aqueous solution?
(CH3)3C-F
The p orbital of the charged carbon in the isopropyl cation, (CH3)2CH+, contains how many electrons?
0
Which alkyl halide would you expect to undergo an SN2 reaction most slowly?
1-bromo-2,2-dimethylbutane
How many moles of hydrogen (H2) will react with cylohexa-2,5-diene-1,4-diol?
2
The neopentyl group has the alternative name:
2,2-Dimethylpropyl
What product is formed when 2,3,3-trimethylhept-1-en-6-yne is reacted with Pd/C and H2?
2,3,3-trimethylheptane
The IUPAC name for diisobutylacetylene is
2,7-Dimethyl-4-octyne
How many alkanes of formula C7H16 possess a quaternary carbon atom?
3
An alkane which can exhibit optical activity is:
3-Methylhexane
What product is formed when 5-chlorocyclohex-3-en-1-ol is reacted with Pd/C and H2?
3-chlorocyclohexanol
CH3CHBrCH2CHClCH3 is the generalized representation of what number of stereoisomers?
4
How many chiral stereoisomers can be drawn for CH3CHFCHFCH(CH3)2?
4
How many compounds with the formula C7H16 (heptanes) contain a single 3° carbon atom?
4
How many different compounds are there which correspond to the general name "3-(1-methylbutyl)cyclobutanol"?
4
How many constitutional isomers are possible for the formula C6H14?
5
What is the index of hydrogen deficiency (or degree of unsaturation) of a compound with the molecular formula of C7H7NOS?
5
What is the index of hydrogen deficiency (or degree of unsaturation) of a compound with the molecular formula of C9H6Br2O2?
6
3-Methyl-5-(1-methylethyl)octane
A correct IUPAC name for the following compound is:
4-bromo-3,6,7-trimethyl-1-octene
A correct IUPAC name for the following compound is:
5-chloro-4-propyl-3-heptanol
A correct IUPAC name for the following compound is:
6-chloro-2-methyl-3-nonene
A correct IUPAC name for the following compound is:
III
A solution of which of these allenes will rotate plane-polarized light?
3-Methyl-4-(1-methylethyl)heptane
An IUPAC name for is:
2-Methylbutyl
An IUPAC name for the group is:
Which of the following is not a good leaving group?
C2H5O-
Which is a polar aprotic solvent?
CH3CH2CH2OCH2CH2CH3
Which is the strongest nucleophile?
CH3CH2O-
It would increase the rate four times.
Consider the SN2 reaction of 2-iodopentane with CH3CO2- ion. Assuming no other changes, what effect on the rate would result from simultaneously doubling the concentrations of both 2-iodopentane and sodium acetate?
staggered and gauche
Consider the graph below, which is a plot of the relative energies of the various conformations of hexane, viewed through the C-2-C-3 bond. The conformations corresponding to the 60o and 300o are:
Top to Bottom: R, S
Determine the R/S configuration for the chiral centers in Compound I.
left to right: 3S, 4R
Determine the R/S configuration for the chiral centers in Compound II.
Which ion is the strongest nucleophile in an aprotic solvent such as dimethylsulfoxide?
F-
Which is the weakest nucleophile in polar protic solvents?
F-
starting material
For the reaction energy diagram below, what structure would be present at point A in the reaction mechanism?
4-Methyl-2-hexyne
Give the IUPAC name for
Select the reagents necessary to convert cyclopentene into cyclopentane.
H2 and Ni
Identify the nucleophile in the following reaction: 2 H2O + RX → ROH + H3O+ + X-
H2O
Which SN2 reaction will occur most rapidly in aqueous acetone solution? Assume concentrations and temperature are the same in each instance.
HO- + CH3-Cl → CH3OH + Cl-
3
How many guache interactions are shown in structure II below?
Which is the weakest nucleophile in polar aprotic solvents?
I-
Which nucleophilic substitution reaction is not likely to occur?
I- + CH3CH2-OH → CH3CH2-I + OH-
H2O
Identify the leaving group in the following reaction.
I-
Identify the leaving group in the following reaction.
Which of the following is true about any (R)-enantiomer?
It is the mirror image of the (S)-enantiomer.
Which of the following solvents will best promote a nucleophilic reaction between NaCN and 1-bromopropane?
MeCN
Which of the following is the poorest leaving group?
NH2-
Which of the following is not a nucleophile?
NH4+
2,4,5-Trimethyl-4-propylheptane
Provide a name for the following compound:
3-sec-Butyl-1-cyclopentanol
Provide a name for the following compound:
5-Bromo-3-chloro-2,3-dimethylhexane
Provide a name for the following compound:
I>IV>II>III>V
Rank the following in terms of nucleophilic strength:
Which of these species, acting in a protic solvent, exhibits greater nucleophilic activity than expected on the basis of its basicity?
SH-
I
Select the potential energy diagram that represents a single-step endothermic (endergonic) reaction.
V
Select the potential energy diagram that represents an exothermic (exergonic) reaction.
II
Select the structure for cis-3-methyl-6-vinylcyclohexene.
Which of the following is not true concerning the strength of a nucleophile?
Strong bases are always good nucleophiles
2R,4R
The Cahn-Ingold-Prelog stereochemical designations used for the following substance are:
3,4,6-Trimethyloctane
The IUPAC name fo
5-cyclobutyl-1-pentanol
The correct IUPAC name for the following compound is:
II
The least stable conformation of butane is:
II
The major product of the following reaction would be:
(2S,3R,4S)-2,4-Dichloro-3-methylhexane
The molecule is properly named:
diastereomers
The molecules below are:
enantiomers
The molecules shown are:
III
The most stable conformation of 1,2-dibromoethane is:
III
The most stable conformation of 2,3-dibromobutane, viewed through the C-2-C-3 bond:
V
The most stable conformation of 3-bromo-2-methylpentane, viewed through the C-2-C-3 bond (i.e., C-2 in the front, C-3 in the back):
Consider the substitution reaction that takes place when (R)-3-bromo-3-methylhexane is treated with methanol. Which of the following would be true?
The reaction would take place with racemization.
A true statement about the transition state(s) of an SN2 reaction is:
The single transition state represents the point of maximum free energy of the reaction.
Which statement is not true for a meso compound?
The stereochemical labels, (R) and (S), must be identical for each stereogenic center.
a single compound.
The structures represent
enantiomers
The two compounds shown below are:
Which statement(s) is/are true about a molecule with the molecular formula C10H20, that when subjected to catalytic hydrogenation there is no consumption of hydrogen?
There is one degree of unsaturation, which happens to be a ring.
(R)-2-methyl-3-butyn-1-ol
What is IUPAC name of the following compound?
2-Ethyl-1-hexanol
What is the correct IUPAC name for the following compound?
3,5-Dimethyl-1-heptanol
What is the correct IUPAC name for the following compound?
3-Bromo-5-Butylcyclohexanol
What is the correct IUPAC name for the following compound?
trans-2-(1-methylethyl)-2-hexen-6-ol
What is the correct IUPAC name for the following compound?
trans-2-(1-methylethyl)-4-hexen-1-ol
What is the correct IUPAC name for the following compound?
7
What is the index of hydrogen deficiency (or degree of unsaturation) for estrogen?
5
What is the index of hydrogen deficiency (or degree of unsaturation) for the drug lidocaine?
trans-4-chlorocyclohexanol
What is the name of the IUPAC name of the following compound?
e
What point on the reaction energy diagram below best indicates the free energy change for the reaction?
II
What product(s) would you expect to obtain from the following SN2 reaction?
II
What structure represents the most stable conformation of cis-1,3-dimethylcyclohexane?
sn1
What type of nucleophilic substitution reaction mechanism is described in the reaction energy diagram below?
IV
Which alkyl halide would be most reactive in an SN1 reaction?
IV
Which compound (I-IV) is a meso compound?
III and IV
Which compound does NOT possess a plane of symmetry?
I
Which conformation represents the most stable conformation of trans-1-bromo-4-methylcyclohexane?
II and III only
Which conformation(s) of 1,2-dibromoethane does not illustrate one or more gauche interactions?
I and V only
Which conformation(s) show(s) the bromines in a gauche orientation for 2,3-dibromobutane, viewed through the C-2-C-3 bond?
More than one of these choices.
Which molecule has a plane of symmetry?
III
Which molecule is achiral?
II, V
Which of the following can be described as cis isomers?
I, III and IV
Which of the following can be described as trans isomers?
II only
Which of the following compounds are chiral?
all of these choices
Which of the following is a conformer of trans-1,2-diethylcyclohexane?
I
Which of the following is a meso compound?
II and V
Which of the following molecules are cis stereoisomers?
I, IV and V
Which of the following represent (R)-2-butanol?
I
Which of the following structures would be the most stable conformer?
V
Which of the following will have the same energy after undergoing ring flip?
IV
Which of these is not a correct Fischer projection formula of the (S) form of 3-bromo-1,1-dichloro-2-propanol?
none of these choices
Which staggered Newman projection(s), looking down the C-2-C-3 bond (C-2 in front and C-3 in back), illustrates the following boxed compound? Cl with 2 solid wedges
III only
Which staggered Newman projection(s), looking down the C-3-C-4 bond (C-3 in front and C-4 in back), illustrate(s) the following boxed compound?
III
Which structure best describes the product of the given reaction when the reaction proceeds via an Sn1 mechanism?
II
Which structure best describes the product of the given reaction when the reaction proceeds via an Sn2 mechanism?
I
Which structure best describes the product of the given reaction?
II
Which structure best describes the product of the given reaction?
More than one of these choices.
Which structure represents (S)-1-chloro-1-fluoroethane?
I
Which structure represents (S)-2-bromobutane?
II and III
Which structure(s) represent(s) diastereomer(s) of I?
Considering the relative solvation of reactants and the transition states of substitution reactions of these reactants, predict which general type of reaction would be most favored by the use of a polar solvent.
Y: + RX → RY+ + X:-
Reaction of (R)-2-chloro-4-methylhexane with excess NaI in acetone gives racemic 2-iodo-4-methylhexane. What is the explanation that best describes this transformation?
an SN1 reaction has occurred due to carbocation formation
An increase in the kinetic energy of reacting molecules results in
an increase in the reaction rate.
The preferred conformation of cis-3-tert-butyl-1-methylcyclohexane is the one in which:
both groups are equatorial.
SN1 reactions of the following type: Nu:- + R-X → R-Nu + :X- are favored
by the use of tertiary substrates (as opposed to primary or secondary substrates) and by use of a weak nucleophile.
SN1 reactions of the following type:Nu:- + R-X → R-Nu + :X-are favored
by the use of tertiary substrates (as opposed to primary or secondary substrates) and by use of a weak nucleophile.
How is it possible to differentiate compounds in a racemic mixture?
chemical conversion to a diastereomeric mixture
I
cis-1,2-Dibromocyclohexane is represented by structure(s):
I
cis-1,3-Dibromocyclohexane is represented by structure(s):
Hexane and 3-methylpentane are examples of:
constitutional isomers.
What product is formed when cyclohexa-2,5-diene-1,4-diol is reacted with Pd/C and H2?
cyclohexane-1,4-diol
What product is formed when trans,trans-hepta-3,5-dien-1-yne is reacted with Pd/C and H2?
heptane2
(2R,4S)-2,4-Dichloropentane and (2S,4R)-2,4-dichloropentane are:
identical
Increasing the temperature of a chemical reaction usually increases greatly the rate of the reaction. The most important reason for this is that increasing the temperature
increases the fraction of collisions with energy greater than Eact.
What product is formed when trans-1,2-dimethylcyclohexane is reacted with Pd/C and H2?
no reaction
Enantiomers are:
non-superposable molecules that are mirror images of each other.
The hybridization state of the charged carbon in a carbocation is ___.
sp2
What is the most thermodynamically stable chair conformation for the substituents on cis-4-tert-butylcyclohexanol?
tert-butyl group equatorial and OH group axial
The most stable conformation of cis-1-tert-butyl-2-methylcyclohexane is the one in which:
the methyl group is axial and the tert-butyl group is equatorial in a chair conformation .
Which one of the following can exist in optically active forms?
trans-1,3-Dichlorocyclohexane
SN1 reactions of the type, Nu- + RL → Nu-R + L-, are favored
when tertiary substrates are used.
Which will be true for any actual or potential nucleophilic substitution reaction?
ΔG‡ is positive.
The difference in the bond energies of reactants and the transition state of a reaction is designated by the notation:
ΔH‡
