UCSanDiego Organic Chemistry Midterm 1 Multiple Choice Questions Solve this worksheet for an organic chemistry class. The worksheet is attached below.Solve

UCSanDiego Organic Chemistry Midterm 1 Multiple Choice Questions Solve this worksheet for an organic chemistry class. The worksheet is attached below.Solve on a separate sheet and send me a scan! Organic II, Midterm 1
Name:
Question 1 (8 points): Multiple choice.
Which of the following would generate a signal with the highest chemical shift in a 1H NMR spectrum?
a.) 1-bromopropane
b.) 2-bromopropane
c.) 1-chloropropane
d.) 2-chloropropane
e.) 1-fluoropropane
How many signal clusters are present in a 1H NMR spectrum of cyclohexanone?
a.) 1
b.) 2
c.) 3
d.) 4
e.) none of the above
If bromocyclohexane is treated with Mg/ether, and then added to water, the product is:
a.) Cyclohexanol
b.) Cyclohexene
c.) Cyclohexane
d.) No reaction—bromocyclohexane is recovered unchanged.
e.) none of the above
The “carbene” formed by heating diazomethane is best described as:
a.) A sp3-hybridized carbon bearing 3 bonded atoms and a negative charge
b.) A sp3-hybrided carbon bearing 3 bonded atoms and no net charge
c.) A sp2-hybridized carbon bearing two bonded atoms and no net charge
d.) A sp-hybridized carbon bearing a positive charge
e.) None of the above
Which of the following nucleophiles can add reversibly to a carbonyl?
a.) Hydroxide ion
b.) Alkyllithium reagents
c.) Grignard (organomagnesium) reagents
d.) Alkynyl anions
e.) None of the above
Which of the following reagents effectively reverses a PCC oxidation when added to an aldehyde?
a.) an alkyllithium reagent
b.) NaBH4
c.) an “ylide”
d.) Zn/Hg, HCl, heat
e.) None of the above
Which of the following is not true of an “ylide?”
a.) It contains an electrophilic carbon atom.
b.) It contains a heteroatom (e.g., phosphorus) bearing a positive charge.
c.) It reacts with carbonyl compounds.
d.) It can be formed in two steps from a haloalkane using Sn2 and acid-base chemistry.
e.) None of the above.
Which of the following is not generally true of tautomers (for example, an enol and a ketone)?
a.) They are related by the shift of a hydrogen atom and a double bond.
b.) They can interconvert in the presence of an acid or base.
c.) They are isomers of each other.
d.) They are equally stable.
e.) None of the above.
Question 2 (22 points): Short answer
a.) When the below compound is treated with aqueous sodium hydroxide, it exists in equilibrium with an
“enolate ion.”
a.) Draw both resonance forms of this ion, and circle the “major” one.
O
b.) Does this equilibrium favor the reactants or the products?
c.) Provide IUPAC names for the following. Include stereochemistry (R/S/E/Z) as appropriate:
Cl
Cl
Cl
H
O
O
O
HO
O
O
d.) Suppose that
were treated with NaBH4. Two isomeric compounds are formed in unequal amounts.
Draw them, and circle the one formed in the greatest amount.
e.) In one sentence, explain why the alkene (vinylic) hydrogens in
Cl
are non-equivalent by NMR.
Question 3 (24 points): Spectroscopy. The spectra given below corresponds to one of the compounds listed
below:
O
a.)
O
b.)
O
c.)
d.)
e.)
O
OH
? Which compound is it?
? In the space above, sketch the compound and label the different kinds of hydrogens that correspond to
different signals in the 1H NMR spectrum.
1H NMR:
For clarity: There are seven signals present
0.8 ppm, triplet, 3H
0.9 ppm, doublet, 3H
1.2 ppm, triplet, 3H
1.4 ppm, quintet, 2H
1.6 ppm, multiplet, 1H
3.2 ppm, doublet, 2H
3.4 ppm, quartet, 2H
? How many signals would you expect to find in a 13C NMR spectrum of this compound?
? How could IR be used to distinguish structure (d) from structure (e)?
? All of the compounds listed above produce the same molecular ion peak by MS. What is its mass?
? The compound corresponding to the given NMR spectrum also produces a strong fragment peak at 59 amu.
Draw the molecule and use a dashed line to indicate the bond that most likely cleaves to form this signal.
Question 4 (21 points): Reaction fluency.
a.) Predict the products formed when
O
reacts with each of the following reagents .
? LiAlH4, then H3O+ workup:
? Ph3P+ – CH2-:
? NH3, cat. H3O+1; then NaBH3CN
Br
?
+ Mg in ether; then H3O+ workup:
? NaCN, HCN:
O
b.) Predict the products formed when
? 1-propanol (large excess), cat. H3O+
? NaOH, then CH3I:
OH reacts with each of the following reagents
Question 5 (32 points): Mechanisms, pt. 1. CHOOSE TWO reactions from the list below to diagram with
proper arrow formalism. If an intermediate has multiple valid resonance structures, be sure to include the best
one.
H
1.)
O
OH
Li , ether
2.) H3O+ workup
i.)
H
N
O
cat. H3O+
N
ii.)
O
iii.)
a.)
b.)
Li
, then H3O+ workup
OH
Question 6 (32 points): Synthesis. CHOOSE TWO. Provide a sequence of reactions to convert the provided
starting materials into the specified products.
OH
i.)
ii.)
iii.)
a.)
b.)
Br
O
Br
O
Question 7 (18 points): Mechanisms, pt. 2. CHOOSE ONE reaction from below to diagram with proper arrow
formalism. If an intermediate has multiple valid resonance structures, be sure to include the best one.
O
i.) O
O
cat. H3O+
O
H
O
H
Br2, cat. H3O+
O
Br
ii.)
O
O
OH
iii.)
(3 eq.)
CH3OH, cat. H3O+
O

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