Organic Chemistry
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In the given reaction, which direction would be more favored with an increase in temperature?
In the acid-base reaction below, determine the ∆G° in kcal/mol at 279 K.
The equilibrium constant (Keq) of a reaction can be calculated using the following equation.
Calculate the equilibrium constant for the following reaction at room temperature (298K).
A. Keq = 6.0
B. Keq = 0.006
C. Keq = 6000
D. Keq = 6.066
(I) Identify the side of the reaction that is favored by entropy. (II) And if the change in entropy (∆S°) is zero for this reaction, calculate the change in Gibbs free energy (∆G°) using the assumption of a temperature (T) of 298 K.
Consider the following equilibrium process and its related ∆G°:
(1) Calculate Keq.
(2) Determine the % reactants and % products present in an equilibrium mixture at 298 K.
Consider the following figure depicting the rotation around the single bond of 1-bromo-2-methylpropane. Determine the rate law expression for this reaction based on the provided experimental data.
Assuming no knowledge of the mechanism of the equilibrium below and given the relevant bond dissociation energies (BDE), estimate the equilibrium constant (in 3 s.f.) for the equilibrium process at 298.15 K.
Relevant BDE values
C―C π bond = 65 kcal/mol3° C―H bond = 91 kcal/mol2° C―H bond = 95 kcal/mol
Assuming all factors are the same, a first-order reaction will occur slower than a second-order reaction. True or False?
Consider the rotation around the single bond of butan-2-ol. Based on experimental observations, what is the order of the reaction with respect to butan-2-ol?
Consider the following reactions A and B:
A:
B:
Determine which reaction will occur more quickly. [Hint: Compare the stability of the bases on the reactant side.]
The following reaction takes place when a small piece of platinum is added to a mixture of propene and hydrogen (H2).
Experimental results show that a change in the concentration of propene or H2 has no effect on the reaction rate.Determine the kinetic order with respect to propene and H2. Find the overall order.
For T1 = 40°C and T2 = 125°C, determine the equilibrium constants and ∆G° if a reaction has ∆H° = 10 kcal/mol and ∆S° = 0.14 kcal/(mol⋅K). How do ∆G° and Keq change as T increases?
If the value of ΔGº for the following reaction is −2.0 kJ/mol (−0.48 kcal/mol), calculate Keq at room temperature (25 °C).CH3CH2Br + H2S ⇌ CH3CH2SH + HBr
A. −0.81
B. 0.44
C. 0.81
D. 2.24
Analyze the provided values below to ascertain whether the reaction would be favorable or unfavorable.
∆H° = +9.45 kcal/mol ; ∆S° = +80 cal/mol•K ; T = 425 K
If the temperature is increased, which direction of the reaction, if any, would be favored?
2-chloro-2-methylbutane reacts with methanol according to the following chemical equation.Experimental results suggest that the reaction follows the rate equation shown below:rate = kt [2-chloro-2-methylbutane]Determine the kinetic order with respect to 2-chloro-2-methylbutane.
Chemical reactions are the result of random collisions. Which of the following will increase the frequency of molecular collisions?
i. adding a catalyst
ii. adding more reactants
iii. increasing the number of steps of the reaction
iv. increasing the temperature
v. decreasing the temperature
Consider a fluorine radical generating a radical from butane. Predict whether the transition state is reactant-like or product-like and justify your answer. [Use the the following bond-dissociation enthalpies.]
In the acid-base reaction below, what is the ∆G° at 380 K?
2-chloro-2-methylbutane reacts with methanol according to the following chemical equation.
The reaction is found to follow the rate equation shown belowrate = kt [2-chloro-2-methylbutane]Determine the overall kinetic order.
In the given acid-base reaction, determine the conjugate base-to-acid ratio. Assume that the concentrations of the reactants are equal.
In the equilibrium (acid-base) reaction below, determine the Gibbs free energy (∆G°) at 289 K.
Determine if the equilibrium constant is going to be greater than, equal to, or less than 1 for the following equilibrium reaction. Justify your answer.
The reaction of methyl bromide with a base is linearly dependent on the concentrations of methyl bromide and OH −. For T = 40°C, the rate constant for such a reaction is 1.2×10 −8/(M•s). Determine the effects of increasing methyl bromide's concentration to 1.50 M on the:
1. Reaction rate
2. Rate constant
Cyclopentene reacts with bromine according to the following chemical equation.
The reaction rate is found to follow the following rate law under certain conditionsrate = kt [cyclopentene] [Br2]2Determine the kinetic order with respect to cyclopentene.
Consider the equilibrium process shown below and its corresponding ∆G°:
(1) What is the equilibrium constant (Keq) of the reaction?
(2) Calculate the % reactants and % products in an equilibrium mixture at 298 K.
1. Which of the following reactions has a greater equilibrium constant?
2. A student starts both reactions with a reactant concentration of 1.0 M. Determine which reaction produces the most product after the reactions have reached equilibrium.
Molecule X reacts in a two-step process to yield molecule Y, with the rate-determining step being the second step. On the other hand, molecule X undergoes a three-step process to yield molecule Z, with the rate-determining step being the first step. Sketch reaction coordinate diagrams for both reactions, clearly illustrating that the reaction leading to the formation of Y occurs at a faster rate compared to the reaction leading to the formation of Z.
The value of ΔG° for the reaction below is −8.20 kJ/mol (−1.96 kcal/mol).
CH3Cl + H2S ⇌ CH3SH + HCl
At 25.0°C, the initial concentrations of CH 3Cl and H2S are both 1.00 M. Determine the equilibrium concentrations of all species.
Cyclopentene reacts with bromine according to the following chemical equation.The reaction rate is found to follow the following rate law under certain conditionsrate = kt [cyclopentene] [Br2]2Determine the kinetic order with respect to bromine.
Given the changes in the concentrations of chloropropane and hydroxide ion, determine its effect on the rate of the reaction.
Alkyl halide concentration is halved and the hydroxide ion concentration is quadrupled.
Consider the following reaction of propan-2-ol and chloroethane:
This reaction occurs through the following mechanism:
Explain why this reaction mechanism is favored and estimate the value of K eq based on the stability of the anions.
Based on the data given below, determine the number of molecules involved in the rate-determining step.
Given the keto-enol tautomerism below, the relevant bond dissociation energies (BDE), and no knowledge of the mechanism, estimate the equilibrium constant (in 3 s.f.) for the reaction at 298.15 K.
C―C π bond = 65 kcal/molC―O π bond = 85 kcal/mol2° C―H bond = 95 kcal/molRO―H bond = 102 kcal/mol
Determine the rate law for the overall reaction if step 1 is the rate-determining step.
Which of the following reactions would proceed at a higher rate? Consider the relative values of the frequency factor (A) to compare the rates.
Fill in the missing rates in the following table that represents the rotation around the single bond of butane. The rate of the reaction is independent of concentration.
A reaction has an enthalpy change of +12.8 kcal/mol and an entropy change of +75 cal/mol⋅K. (a) At which temperature will the process be in a state of neither being favored nor disfavored? (b) Will the process be favored or disfavored if the temperature exceeds the calculated value? (c) And what about if the temperature is lower than the calculated value?
Given the changes in the concentrations of chloroethane and hydroxide ion, determine its effect on the rate of reaction.Alkyl halide concentration is doubled and the hydroxide ion concentration is quadrupled.
True or False: When rotating around a bond, the rate constant and the reaction rate are equal to zero. Justify your answer.
Is the equilibrium constant going to be greater than, equal to, or less than 1 for the following equilibrium reaction? Explain.
Determine from the given thermochemical values (∆H°, ∆S°, and T) if the reaction will be favorable or unfavorable.
∆H° = -9.2 kcal/mol ; ∆S° = -21 cal/mol•K ; T = 298 K
Determine the enthalpy (∆H°) of the equilibrium process given below.
What is the enthalpy (∆H°) of the following process?
Assuming the T = 298 K, determine the ∆G°, ∆H°, and ∆S° for the following reaction. Base the value of enthalpy (∆H°) on the structure of the conjugate bases.
Determine the probable transition state of the given reaction. Make sure to indicate which bond is broken or formed.
What is the probable transition state of the given reaction? Make sure to indicate which bond is broken or formed.
Predict the probable transition state of the given reaction. Make sure to show which bond is broken or formed.
What is the ∆H° for the reaction below?
At 25 °C, what is the ∆G° for the conversion of "axial" isopropylcylcohexane to "equatorial" isopropylcylcohexane?
At equilibrium, what percentage of ethylcyclohexane has its ethyl substituent in an equatorial position? (ΔG° for the conversion of equatorial ethylcyclohexane to axial ethylcyclohexane at 25°C is −1.81 kcal/mol)
When used as local anesthetics, it takes a longer time for one-half of etidocaine to be metabolized than tetracaine. Explain why.
The intramolecular reaction of the cis alkene (Reaction A) is relatively faster than the intermolecular reaction (Reaction B). Suppose a trans alkene undergoes a similar reaction. Which of the two reactions will its rate be similar?
Reaction A
Reaction B
If reactant X and product Y are in equilibrium, determine the relative amounts of X and Y present at 30°C when (i) ∆G° = 4.76 kcal and (ii) ∆G° = 0.78 kcal.
If reactant X and product Y are in equilibrium, what are the relative amounts of X and Y present at 27°C when (i) ∆G° = −4.60 kcal and (ii) ∆G° = −0.97 kcal?
At 28.9°C, the reaction between a certain alkyl halide and the −OH has a ΔG° value of −24.9 kcal/mol. Determine the reaction's equilibrium constant (Keq).
Uncatalyzed decarboxylation of the oxaloacetic acid dianion has a rate constant of 1.7×10–5 s–1. The rate constant becomes 0.17 s–1 in the presence of Zn(II). To what extent does the catalyst accelerate the rate of reaction?
Which properties are affected when a reaction is performed with a catalyst compared to the same reaction without a catalyst?
∆G°, ∆H‡, Ea, ∆S‡, ∆H°, Keq, ∆G‡, ∆S°, k
True or False: Increasing the stability of the reactant or decreasing the stability of the transition state will increase the rate constant of the reaction.
Using the Arrhenius equation, determine if the rate constant of a reaction would increase, decrease, or remain unchanged when the activation energy is increased.
Using the Arrhenius equation, predict whether the rate constant will increase, decrease, or remain unchanged when the reaction temperature is increased.
In the presence of a base, two molecules of pentan-3-one can condense to form a hydroxy ketone. Assuming that pentan-3-one has an initial concentration of 1.00 M and that about 10.0% of pentan-3-one is converted to the hydroxy ketone product at room temperature, estimate the value of ΔG°.