Ch. 5: Alkenes Flashcards
(39 cards)
An alkene is (1) ____________________ . Because alkenes contain fewer than the maximum # of hydrogens, they are called
(2) ________________________ .
(1) a hydrocarbon that contains a double bond.
(2) unsaturated hydrocarbons.
The double bond is the __________ , or center of reactivity, of an alkene.
functional group
The general molecular formula for a hydrocarbon is __________ , minus 2 hydrogens for every pi bond or ring in the molecule.
CnH2n+2
The number of pi bonds plus the # of rings is called the _______________ .
degree of unsaturation
When there are both a functional group suffix and a substituent, which one gets the lowest possible number?
The functional group suffix gets the lowest possible number.
What is the difference between the Z isomer and the E isomer? What do priorities mean in this context?
The Z isomer has the high-priority groups on the same side of the double bond.
The E isomer has the high-priority groups on opposite sides of the double bond.
The relative priorities depend on the atomic numbers of the atoms bonded directly to the sp2 carbon.
All compounds with a particular _____________ react in the same way.
functional group
Due to the cloud of electrons above and below the pi bond, an alkene is a __________.
nucleophile
What is the name for the electron-deficient species, opposite to nucleophiles?
Electrophiles are the electron-deficient species. Nucleophiles are attracted to them.
What kind of reactions do alkenes undergo?
Alkenes undergo electrophilic addition reactions.
What do curved arrows indicate in reactions?
Curved arrows show the bonds that are formed and the bonds that are broken in a reaction.
Thermodynamics vs. kinetics
Thermodynamics describes a reaction at equilibrium.
Kinetics describes how fast the reaction occurs.
What is a reaction coordinate diagram?
A reaction coordinate diagram shows the energy changes that occur during the course of a reaction.
The more stable a species, the _________ its energy.
lower
What is the state that is in limbo between reactants and products?
As reactants are converted into products, a reaction passes through a maximum-energy transition state.
What is formed between a reactant and a product?
An intermediate.
Transition state vs. intermediate
A transition state has partially formed bonds while an intermediate has fully formed bonds.
The _________________ has its transition state at the highest point on the reaction coordinate.
rate-determining step
What is Keq?
Keq represents the equilibrium constant which is found by the concentrations of the products divided by the concentrations of the reactants.
Define Le Chatelier’s principle.
Le Chatelier’s principle states that if an equilibrium is disturbed, the system will adjust to offset the disturbance.
What is the Keq value and the sign of free energy (delta G) when the reaction is exergonic? When the reaction is endergonic? What is the relationship between products and reactants in these 2 cases?
When the reaction is exergonic, Keq > 1, free energy is negative, and the products are more stable than the reactants.
When the reaction is endergonic, Keq < 1, free energy is positive, and the reactants are more stable than the products.
What is the formula for Gibbs free-energy change (delta G)?
delta G = delta H - T * delta S, where delta G = Gibbs free-energy change, delta H = change in enthalpy, T = temperature in Kelvin, delta S = change in entropy.
What does delta H stand for?
Delta H is change in enthalpy, which is the heat given off or consumed as a result of bond making and bond breaking.
What kind of reaction has a negative delta H?
What kind of reaction has a positive delta H?
An exothermic reaction has a negative delta H.
An endothermic reaction has a positive delta H.
