Consider the ring-flip equilibrium experienced by trans-1,4-difluorocyclohexane. Write the equilibrium such that the least stable chair...

Consider the ring-flip equilibrium experienced by trans-1,4-difluorocyclohexane. Write the equilibrium such that the least stable chair conformation is the product (this will cause the ΔE to be greater than (or equal to) zero.

T = 298 K
R = 8.315 J/mole-K

H - Substituent Interaction	1,3-Diaxial Strain (kJ/mole)
H ←→ F	0.5
H ←→ OH	2.1
H ←→ CH₃	3.8
H ←→ CH₂CH₃	4.0

ΔE - Enter a number greater than (or equal to) zero     (Tol: ± 0)
Enter the value of k_eq (solve ΔE = -RTlnk_eq)     (Tol: ± 0.01)
Estimate % most stable conformer from graph (page 120)     (Tol: ± 3)
Estimate % least stable conformer from graph (page 120)     (Tol: ± 3)
Calculate % most stable conformer from k_eq     (Tol: ± 1)
Calculate % least stable conformer from k_eq     (Tol: ± 1)

Expert Solution

PART 1: Consider the ring-flip equilibrium experienced by trans-1,4-difluorocyclohexane. Write the equilibrium such that the least stable chair conformation is the product (this will cause the ΔE to be greater than (or equal to) zero.

ANS: Conformation and sterioisomerism of trans-1,4-difluorocyclohexane.

trans-1,4-difluorocyclohexane, the diequatorial is the mosts stable arrangement is the "trans" isomer. Ring flipping of trans-1,4-difluorocyclohexane gives a conformation in which the fluro substituents are anti (dihedral angle of 180) to each other, but this is still trans, and this conformation is less stable because it has two axial substituents.

PART 2: T = 298 K; R = 8.315 J/mole-K

H - Substituent Interaction	1,3-Diaxial Strain (kJ/mole)
H ←→ F	0.5
H ←→ OH	2.1
H ←→ CH3	3.8
H ←→ CH2CH3	4.0

ΔE - Enter a number greater than (or equal to) zero (Tol: ± 0)

Enter the value of keq (solve ΔE = -RTlnkeq) (Tol: ± 0.01)

Estimate % most stable conformer from graph (Tol: ± 3)

Estimate % least stable conformer from graph (Tol: ± 3)

Calculate % most stable conformer from keq (Tol: ± 1)

Calculate % least stable conformer from keq (Tol: ± 1)

ANS:

H - Substituent Interaction	1,3-Diaxial Strain (kJ/mole)	2Diaxial Strain	keq	Axil : equatorial isomer
H ←→ F	0.5	1	- 0.404	1 : 2.5
H ←→ OH	2.1	4.2	- 1.69	1 : 0.6
H ←→ CH3	3.8	7.6	- 3.067	1 : 0.4
H ←→CH2CH3	4.0	8	- 3.229	1 : 0.3

*The axial isomer of isopropylcyclohexane contains two 1,3-diaxial interactions between isopropyl and hydrogen whereas the equatorial isomer of isopropylcyclohexane contains none. Thus, the axial isomer is

(2 x 0.12) kcal/mol = 0.24kcal/mol higher in energy and the equatorial isomer is favored.

ΔE = -RTlnkeq

keq = e(–∆E/ RT)

keq = e (1000)(8.315298) = 0.404

To get to whole number to obtain axil and equatorial ratio,

0.404 1

-------- : --------- = 1 : 2.5

0.404 0.404

Thus, the ratio of axial to equatorial (H ←→ F) that is present at 298k is ~ 1 : 2.5

I need more details to Estimate % most stable conformer from graph (Tol: ± 3)

Estimate % least stable conformer from graph (Tol: ± 3).

queen_honey_blossom answered 2 years ago

Draw both cis- and trans-1,4-dimethylcyclohexane in their more stable chair conformations

Draw both cis- and trans-1,4-dimethylcyclohexane in their more stable chair conformations. (a) How many stereoisomers are there of cis-1,4-dimethylcyclohexane, and how many of trans-1,4-dimethylcyclohexane? (b) Are any of the structures chiral? (c) What are the stereochemical relationships among the various stereoisomers of 1,4-dimethylcyclohexane?

What is the barrier to rotation about the C-C bond in ethane? Consider the structure of trans-1,4-dimethylcyclohexane. Which statemen is fully correct?

What is the barrier to rotation about the C-C bond in ethane? A. about 1.0 kcal/mol B. about 3.0 kcal/mol C. about 2.0 kcal/mol D. about 2.5 kcal/mol Consider the structure of trans-1,4-dimethylcyclohexane. Which statemen is fully correct? A. Trans methyl groups favor chair and both are equatorial. B. Trans methyl groups favor chair and both are axial. C. Trans methyl groups favor twist-boat conformation. D. Trans methyl groups favor chair and are axial and equatorial.

Consider the equilibrium Na2O(s) + SO2(g) ⇌ Na2SO3(s). (a) Write the equilibrium-constant expression for this reaction in terms of partial pressures.

Consider the equilibrium Na2O(s) + SO2(g) ⇌ Na2SO3(s).(a) Write the equilibrium-constant expression for this reaction in terms of partial pressures.(b) All the compounds in this reaction are soluble in water. Rewrite the equilibrium-constant expression in terms of molarities for the aqueous reaction.

Consider 100 g mass hung from a spring at equilibrium (y = 0). Write the equation...

Consider 100 g mass hung from a spring at equilibrium (y = 0). Write the equation of oscillation, and sketch of the mass’ position y(t) for the following situations. Be sure to correctly identify each function drawn. a) Suppose the mass is displaced upward from the equilibrium position by 10 cm and then released from this position at time t = 0. A period of oscillation of 2 second was observed. Draw this on the first graph. (b) Suppose the...

Question