KEY...1,2-butanediol e. 4-mercapto-1-butanol Water can act as the hydrogen bond donor ... Which...
Transcript of KEY...1,2-butanediol e. 4-mercapto-1-butanol Water can act as the hydrogen bond donor ... Which...
Chemistry 262
Quiz 1
Winter 2018
The following quiz contains 30 questions valued at 3 point/question, and 4 bonus
problems valued at 1 point/question, and space for you to demonstrate 3 2-step
functional group interconversions at 1 point each.
Name: KEY
CLASSIFICATION OF ALKYL HALIDES, ALCOHOLS, THIOLS, ETHERS, AND SULFIDES
1. Which of the following is benzyl methyl sulfide?
a.
b.
c.
d.
e.
The dreaded benzyl (as opposed to phenyl) group
NOMENCLATURE OF ALKYL HALIDES, ALCOHOLS, THIOLS, ETHERS, AND SULFIDES
2. The correct IUPAC name for tert-butyl alcohol is
a. 1-butanol
b. 2-methyl-1-propanol
c. 2-methyl-2-propanol
d. 2-butanol
e. 1,1-dimethyl-1-ethanol
Hard to believe so many forgot about assigning the longest parent chain
NOMENCLATURE OF ALKYL HALIDES, ALCOHOLS, THIOLS, ETHERS, AND SULFIDES
3. Which of the following is the correct structure for the compound commonly referred
to as dioxane?
a.
O
b.
O
c.
d.
e.
None of the above corresponds to dioxane
Dioxane is also known as 1,4-dioxacyclohexane, or [6]-crown-2
HOMOGENEOUS INTERMOLECULAR INTERACTIONS – BOILING POINTS AND MELTING POINTS
4. Which of the following would have the greatest boiling point?
a. (CH3)3CCl
b. (CH3)3COH
c. (CH3)3COK
d. (CH3)2CHOCH(CH3)2
e. CH3CH2CH2CH2OH
Really should be a straightforward problem once the metal atom indicating ionic bonding
has been identified
HOMOGENEOUS INTERMOLECULAR INTERACTIONS – HYDROGEN BONDING
5. Which of the following compounds has the highest boiling point?
a. Hexane (MW = 86, BP = 69 oC)
b. Glycerol (1,2,3-propanetriol) (MW = 92 g/mol, BP = 290 oC)
c. Propylene glycol (1,2-propanediol) (MW = 76, BP = 188 oC)
d. Isobutyl alcohol (MW = 74, BP = 108 oC
e. Ethylene glycol (MW = 62 g/mol, BP = 197 oC)
Largest with the most extensive hydrogen bonding network
HOMOGENEOUS INTERMOLECULAR INTERACTIONS – MELTING POINTS
6. Xylene is another name for the dimethyl benzenes. Which of the following would have
the highest melting point?
a. ortho-xylene
b. meta-xylene
c. para-xylene
d. ethylbenzene
e. toluene
Largest with the most extensive hydrogen bonding network
HETEROGENEOUS INTERMOLECULAR INTERACTIONS – SOLUTIONS AND SOLUBILITY
7. Which of the following solvents would dissolve NaCl to the greatest extent?
a. Hexane ( = 1.9)
b. Dichloromethane ( = 8.9)
c. Diethyl ether ( = 4.3)
d. Ethyl Acetate ( = 6.0)
e. Formic acid ( = 59)
Please see table 8.2. NaCl is highly soluble in formic acid (95 % HCO2H, 58 g/100 mL)
HETEROGENEOUS INTERMOLECULAR INTERACTIONS – SOLUTIONS AND SOLUBILITY
8. Which of the following has the greatest solubility in water?
a. Pentane
b. Diethyl ether
c. Dichloromethane
d. n-propyl chloride
e. None of the solvents listed dissolves > 0.1 % w/v
4:1 C to O ratio gives saturation at 6.0 g/100 mL or since d = 0.71 g/mL or 8.4 % v/v
Diethyl ether has a lower dipole moment and dielectric constant than dichloromethane, but
can hydrogen bond with water. Dichloromethane’s solubility limit is 1.8 g/100 mL @ 25 oC
HETEROGENEOUS INTERMOLECULAR INTERACTIONS – SOLUTIONS AND SOLUBILITY
9. Which of the following compounds would have the poorest water solubility?
a. Diethyl sulfide
b. Diethyl ether
c. 1-butanol
d. 1,2-butanediol
e. 4-mercapto-1-butanol
Polarizable yes, polar no, hydrogen bonding no – diethyl sulfide is insoluble in water.
Being polarizable, it has a boiling point of 92 oC. For comparison, with a molar mass =
90 g/mol, a similarly sized hexane (MW = 86) boils at 69 oC, similarly sized pentanol
(MW = 88) boils at 138 oC…the power of hydrogen bonding
HETEROGENEOUS INTERMOLECULAR INTERACTIONS – SOLUTIONS AND SOLUBILITY
10. Which of the following compounds would have the greatest solubility in water?
a. Diethyl sulfide
b. Diethyl ether
c. 1-butanol
d. 1,2-butanediol
e. 4-mercapto-1-butanol
Water can act as the hydrogen bond donor – a Godsend, since all we have to do is
establish the C:O ratio as a first approximation (but be on the lookout for esters).
Again, thiols or thioethers cannot hydrogen bond, but thiols can be ionized. Pay
attention to high pH conditions
HETEROGENEOUS INTERMOLECULAR INTERACTIONS – HOST/GUEST RELATIONSHIPS
11. Please name the following compound
Name: [15]-crown-5
BONUS (1 EC): THE COMPOUND SHOWN BELOW WAS AN UNFORTUNATE SIDE PRODUCT IN THE
MANUFACTURE OF THE BROADLEAF HERBICIDE 2,4,5-T ((2,4,5-TRICHLOROPHENOXY)ACETIC ACID,
ANALOGOUS TO 2,4-D SHOWN ON PAGE 441 OF YOUR TEXT). THE SIDE PRODUCT WAS NOT REMOVED
FROM THE PRODUCT MIXTURE, AND A COMBINATION OF 2,4,5-T AND 2,4-D CONSTITUTED THE VIETNAM
DEFOLIANT AGENT ORANGE. THE SIDE PRODUCT IS A WELL-ESTABLISHED DEVELOPMENTAL TOXIN AND
CARCINOGEN AND GOES BY THE NAME TCDD. WHAT DOES THE ACRONYM TCDD STAND FOR?
TCDD: TetraChloroDibenzoDioxin
A benzene attached at 2 places is a benzo group. Obviously, I would have accepted
dioxane instead of dioxin
NUCLEOPHILIC SUBSTITUTION AND -ELIMINATION REACTIONS - OVERVIEW
12. What is the name of the functional group formed when the conjugate base of a
butanethiol displaces iodine from iodobutane in an SN2 reaction?
a. Thiol
b. Thiolate
c. Thioether
d. Sulfide
e. (c) & (d)
A deprotonated thiol is a good nucleophile. Since this happens readily (pKa thioethane =
10.6, this is a common motif in biochemistry)
BONUS (1 EC): NAME THE COMPOUND FORMED
NAME: Dibutyl sulfide, Dibutyl thioether
NUCLEOPHILIC SUBSTITUTION AND -ELIMINATION REACTIONS – REACTION RATES
13. The rate equation for a nucleophilic substitution reaction of a tertiary alkyl bromide (R-
Br) with I ion would be
a. Rate = k [RBr]
b. Rate = k [I]
c. Rate = k [RBr][I]
d. Rate = k [RBr]2[I]
e. Rate = k [RBr][I]2
Tertiary alkyl halide – think SN1 or E1 (in this case iodide is a poor base and thus SN1 is
favored). It is always the formation of the carbocation that is rate limiting in these
reactions.
NUCLEOPHILIC SUBSTITUTION AND -ELIMINATION REACTIONS – REACTION RATES
14. Which of the following statements is/are true of SN1 reactions of alkyl halides in
general?
a. The rate of an SN1 reaction depends on the concentration of the alkyl
halide
b. The rate of an SN1 reaction depends on the concentration of the nucleophile
c. SN1 reactions of alkyl halides occur faster in polar aprotic solvents compared to
protic solvents
d. Statements (a) and (c) are true
e. Statements (a) (b) and (c) are true
Given carbocation formation is always rate limiting, if (b) were true it couldn’t be SN1.
Polar protic solvents give rise to the greatest forces of intermolecular interaction with ions
and so work best to promote unimolecular reactions by stabilizing the transition state
NUCLEOPHILIC SUBSTITUTION AND -ELIMINATION REACTIONS – TRANSITION STATE THEORY
15. For the typical SN2 reaction Y + RX RY + X, it can be predicted S‡ will
be
a. > 0
b. = 0
c. < 0
d. 0
e. Unpredictable as to algebraic sign
In an SN2 reaction, the reactants are part of a single complex – as such, the number of
moles decreases and the entropy decreases
BONUS (1 EC): THE RELATIVE NUCLEOPHILICITIES OF SPECIES DO NOT NECESSARILY PARALLEL THE
RELATIVE BASICITIES OF THE SAME SPECIES BECAUSE
a. NOT ALL NUCLEOPHILES ARE BASES, AND VICE VERSA
b. EXPERIMENTAL MEASUREMENTS OF SUFFICIENT ACCURACY ARE NOT AVAILABLE TO MAKE THE
COMPARISONS
c. NUCLEOPHILICITY IS A THERMODYNAMIC MATTER; BASICITY IS A MATTER OF KINETICS
d. BASICITY IS A THERMODYNAMIC MATTER; NUCLEOPHILICITY IS A MATTER OF
KINETICS
e. ACTUALLY, THE RELATIVE VALUES DO PARALLEL ONE ANOTHER
Ask yourself, “What does the Ka in pKa actually represent?”
NUCLEOPHILIC SUBSTITUTION AND -ELIMINATION REACTIONS – THE SN2 REACTION
16. What is the principal product of the following reaction?
CH2Cl
H OCH3
CH3
OH
CH2OH
H3CO H
CH3
CH2Cl
HO H
CH3
I
III IV
CH2Cl
H OH
CH3
II
CH2OH
H OCH3
CH3
SN2?
a. I
b. II
c. III
d. IV
e. An equimolar mixture of I and II
Semi-tricky I suppose, but the attack is not on a chiral center.
NUCLEOPHILIC SUBSTITUTION AND -ELIMINATION REACTIONS – THE SN2 REACTION
17. When 1,4-diiodo-2,2-dimethylbutane (0.10 mol) is treated with 0.10 mol of NaCN in
dimethyl sulfoxide at 30 C, the product(s) formed is/are
a.
NCI
b.
ICN
That extra C “spacer” makes a big difference (see table 9.3)
c.
NCCN
d.
I
e. Both (a) and (b) in equal amounts
NUCLEOPHILIC SUBSTITUTION AND -ELIMINATION REACTIONS – STEREOCHEMISTRY
18. What would be the major product(s) of the following reaction?
a. I
b. II
c. III
d. IV
e. None of the above
2o alkyl halide, no -substituents, weak base, decent nucleophile in acetone (recall SN2
reactions speed up in aprotic polar solvents). SN2 – look for inversion of configuration
NUCLEOPHILIC SUBSTITUTION AND -ELIMINATION REACTIONS – CRITICAL FACTORS
19. Which of the following is not a polar aprotic solvent?
a.
H3CC
CH3
O
b. H3C C N
c.
H3CS
CH3
O
d.
HC
N
O
CH3
CH3
e.
H3CCH
OH
CH3
It’s an alcohol – analogous to water, yes?
BONUS (1 EC): TO THE RIGHT OF THE STRUCTURE, WRITE THE COMMON NAME OF EACH SOLVENT; IF THE SOLVENT
GOES BY AN ACRONYM, INCLUDE IT AS WELL
I II III IV
Br
I II
NaI
Acetone
NUCLEOPHILIC SUBSTITUTION AND -ELIMINATION REACTIONS – CRITICAL FACTORS
20. Which alkyl halide would you expect to react most slowly when heated in aqueous
solution?
a. (CH3)3C-F
b. (CH3)3C-Cl
c. (CH3)3C-Br
d. (CH3)3C-I
e. They would all react at the same rate
Probably the one with far and away the worst leaving group
NUCLEOPHILIC SUBSTITUTION AND -ELIMINATION REACTIONS – E2 ELIMINATION STEREOCHEMISTRY
21. What is the principal product of the following reaction?
a.
b.
c.
d.
e.
Anti periplaner reaction mechanism, concerted: (1) rotate C2 so Cl is in the plane of the
paper down (2) rotate C3 so H (no shown obviously) is in the plane of the paper up – this
puts methyl groups on opposite sides (3) collapse to alkene, retaining relative positions
Cl
EtOH, EtONa
heat
OEt
NUCLEOPHILIC SUBSTITUTION AND -ELIMINATION REACTIONS – E2 REGIOCHEMISTRY
22. What is major product outcome for the following reaction?
a.
b.
c.
d.
e.
Question is a bit silly at some levels (SN2 inversion followed by elimination) but does
show how care must be taken when planning a synthesis. tBuOK gives the anti-Zaitsev
(least substituted) alkene product. Note the initial position of the Cl (d) is the product
rotated 180o
NUCLEOPHILIC SUBSTITUTION AND -ELIMINATION REACTIONS – FACTORS INFLUENCING SN1 AND E1 REACTIONS
23. Carbocations are frequent intermediates in acidic reactions of alkenes, alcohols, etc.
Which of the following is characteristic of carbocations?
a. Rearrangement to a more stable carbocation
b. Loss of a proton to form an alkene
c. Combination with a nucleophile
d. Reaction with an alkene to form a larger carbocation
e. All of the above
This is actually a decent summary of the behavior of carbocations
Cl
1. NaI, acetone
2. t-BuOH, t-BuOK
NUCLEOPHILIC SUBSTITUTION AND -ELIMINATION REACTIONS – FACTORS INFLUENCING SN1 AND E1 REACTIONS
24. Which mechanistic step in the acid-catalyzed dehydration of 3,3-dimethyl-2-butanol is
the rate determining step?
a.
b.
c.
Step 3:
d.
Step 4a:
+ H3O+
+ H2O
e.
Step 4b:
+ H3O++ H2O
Again, carbocation formation is the rate determining step – recall the analogy of the
impatient, strong, base or nucleophile that is not going to wait around for carbocations
to form, but who is blocked by the tertiary structure which provides enough time for
the more stable (and thus more stable transition state faster) tertiary carbocation to
form. Also recall the treatment of partial inversion that occurs figure 9.13
OH
+ H3O+
OH2
+ H2O
Step 1:
OH2
+ H2O
Step 2:
NUCLEOPHILIC SUBSTITUTION AND -ELIMINATION REACTIONS – GENERAL PRODUCT PREDICTIONS 5
25. What is the major product of the reaction between methanol and (2R,3S)-2-bromo-
3-methylpentane at room temperature?
a.
b.
c.
d.
e. Both (a) and (c)
(1) Draw out the structure. (2) Assess the structure – substitution slows down SN2
reaction (3) Do I have a good base? Nope (4) Is the system being heated to promote
elimination? Nope (5) Are there any other potential nucleophiles around? Nope – looks
like a solvolysis reaction proceeding through a carbocation with the potential to
rearrange to a 3o carbocation
NUCLEOPHILIC SUBSTITUTION AND -ELIMINATION REACTIONS – GENERAL PRODUCT PREDICTIONS
26. What is the principal product outcome for the following reaction?
a.
b.
c.
OCH3
H3CO
ClEtOH, heat
OEt
d.
e.
Assess as for #25, only heat promotes elimination, and ring expansion relieves ring
strain and provides a tertiary carbocation prior to elimination
NUCLEOPHILIC SUBSTITUTION AND -ELIMINATION REACTIONS – GENERAL PRODUCT PREDICTIONS
27. What would be the principal product for the following reaction?
HH3C
H Br
HH3C
H CN
CNH3C
H Br
I II
III IV
CNH3C
H H
HH3C
NC Br
C
25oC
a. I
b. II
c. III
d. IV
e. Equal amounts of I & II
Good nucleophile at room temperature with 2o alkyl halide with no blockers (that my
friends, is humor of the highest order) – straight up SN2 with inversion of configuration
ORGANOMETALLIC COMPOUNDS – FORMATION OF GRIGNARD AND ORGANOLITHIUM REAGENTS
28. Which of the following solvents would be least effective in generating a Grignard
reagent?
a. I
b. II
c. III
d. IV
e. V
No non-bonded pairs of electrons, no Grignard reagent formation
ORGANOMETALLIC COMPOUNDS – REACTIONS OF GRIGNARD AND ORGANOLITHIUM REAGENTS
29. What is the structure of product (D) in the following reaction sequence?
a.
b.
c.
d.
e.
CH3CH2OCH2CH3O
(CH3CH2)3N
CH3(CH2)4CH3 CH3OCH2CH2OCH3
I II III
IV V
CH3CHOH
CH3
CH2
O
CH2
PBr3A
etherB C
H3O+
DMg
CH3CHOCH2CH2OH
CH3
CH3CHCH2CH2Br
CH3
CH3CHCH2CH2OH
CH3
CH3CHOCH2CH3
CH3
CH3CHCH2CH3
CH3
Now would be a good time to start counting carbons. In case it isn’t perfectly clear,
the purpose of the Grignard reaction is to form carbon to carbon bonds. By using PBr3
to convert an alcohol to an alkyl halide, you remove the alcohol from the “main chain”.
By coupling the Grignard reagent to oxirane (epoxide) you extend your carbon chain by 2
carbons. Opening the strained ring by nucleophilic attack gives an alkoxide…or alcohol
upon exposure to acid
CARBENES, CARBENOIDS, AND THE SIMMONS-SMITH REACTION
30. What is the major product for the following reaction?
a.
b.
c.
d.
e.
More than one of the above
Simmons-Smith reaction, a concerted syn addition to alkenes to form cyclopropane rings
I2CH2
Zn(Cu)
I I
I
BONUS: 2 STEP TRANSFORMATIONS
Please neatly list up to 3 2 step functional group interconversions you have learned. You
must proceed from the initial functional group to a second functional group and then in the
2nd reaction from the 2nd functional group to a 3rd. Full credit will be given for
transformations that include conditions
Interconversion 1
Reaction 1:
Reaction 2:
Interconversion 2
Reaction 1:
Reaction 2:
Interconversion 3
Reaction 1:
Reaction 2: