Problem Set # 1
CHEM 8322/4322
Due 1-23-2017
Page 1 of 2
CHEM 8322/4322
January 18, 2017
Problem Set #1
T. R. Hoye
Due in class, Monday January 23, 2017
Detailed Mechanism Provide a detailed mechanism [i.e., explicitly show (using curly arrows) EVERY
intermediate, formal charge (where relevant), equilibrium, and bond-making and -breaking step] to
account for:
(a) the acid-catalyzed conversion of the furan 1 to the ketal/ketone 2.
p-TsOH (cat.)
Me
O
PhH, reflux
OH OH
O
O
O
Me
1
2
(b) the acid-catalyzed cyclization of the diketone 3 to the enone 4 as the major product.
O
O
Me
Me
p-TsOH (cat.)
Me
O
Me
PhH, reflux
3
4
(c) the base-catalyzed cyclization of the same ketone 3 to the conjugated enone 5 as the major product.
O
O
O
Me
NaOMe
Me
Me
MeOH, reflux
3
5
(d) the formation of the dimethylaminomethylidenedione 8 from dimedone (6) and DMF dimethyl
acetal (7). (Hints: 7 initially dissociates to an ion pair in solution and two moles of methanol are
formed as the byproduct for each mole of dimedone that is converted to 8.)
N
DMF
O
O
O
+
N
(solvent)
O
O
O
120 °C
6
7
8
In most cases mechanisms of reactions proceeding under acid (or cationic) conditions involve only
neutral or positively charged intermediates* [and mechanisms of reactions proceeding under basic (or
anionic) conditions involve only neutral or negatively charged intermediates*].
(* those species derived from the organic starting material. Of course, since charge is neither created
nor destroyed, there is always a counterion of opposite charge present to balance the cationic or
anionic charged intermediate.)
Problem Set # 1
CHEM 8322/4322
Due 1-23-2017
Page 2 of 2
Other Problems
1. Draw the structure of p-TsOH, PhH, NaOMe, and DMF. You will see many reagent, catalyst, and
solvent acronyms throughout the semester. It is important that you know what each is. If you are
unfamiliar with any that you see, it is incumbent upon you to look it up. Google is a big help here.
2. trans-1-(Methyl)ethyl-2-methylcyclohexane (9) will exist in predominantly two chair conformers,
9-dieq and 9-diax, each dominated, in turn, by a single rotamer about the cyclohexyl to isopropyl
group C-C bond.
(a) Draw the most stable rotamer with respect to the isopropyl-to-cyclohexane carbon-carbon
bonds for each of these chair conformers (i.e., add the set of Me, Me, and H groups to each of the
dotted bonds in 9-dieq and 9-diax). There should be no 1,7-H,H interactions.
(b) Carefully indicate all of the gauche (1,6-H,H) interactions that exist in each rotamer you have
drawn.
(c) Assuming 0.9 kcal/mol of destabilization for each butane gauche-like interaction, estimate the
equilibrium ratio of 9-dieq to 9-diax at room temperature (recall that ΔG0 = -RTlnKeq).
H
H
H
H
Me
Me
H
H
9
9-dieq
9-diax
3. Consider the hydrocarbon 1-(1-ethylpropyl)cyclohexane [cyc-C6H11CH(Et)2].
(a) Draw an all-staggered conformation that has no syn-pentane interactions.
(b) Draw an all-staggered conformation that has one syn-pentane interaction.
(c) Draw an all-staggered conformation that has two syn-pentane interactions.
(d) Draw two different all-staggered conformations, each of which has three syn-pentane
interactions.
Use a(n imaginary) diamond lattice as a template.