CHEM 331 Exam 2

Acid

Proton donor

Base

Proton acceptor

Conjugate base

Formed when an acid donates a proton to a base

Conjugate acid

Formed when a base accepts a proton from an acid

Acid dissociation constant

A constant used to express the strength of an acid

Reaction mechanism

Sequence of steps occurring during a reaction

Thermochemistry

Study of the energy of an entire system at every instant of a reaction

Transition state

An activation complex with partially broken and partially formed bonds

Reaction coordinate diagrams

Diagrams that show changes in energy for molecules involved in a chemical reaction

Change in Gibbs free energy

Difference in Gibbs free energy between reactants and products

Exergonic reaction

A favorable reaction with a negative change in Gibbs free energy

Endergonic reaction

An unfavorable reaction with a positive change in Gibbs free energy

Enthalpy

Energy contained in chemical bonds and solvation

Heat of reaction

Difference in enthalpy between reactants and products

Exothermic reaction

A reaction that releases heat because the product bonds are stronger than the reactant bonds

Endothermic reaction

A reaction that absorbs heat because the product bonds are weaker than the reactant bonds

Inductive effect

Polarization of the electron density of a covalent bond caused by the electronegativity of a nearby atom

Lewis acid (electrophile)

A molecule or ion that forms a new covalent bond by accepting a pair of electrons

Lewis base (nucleophile)

A molecule or ion that forms a new covalent bond by donating a pair of electrons

Arenes

Benzene and its derivatives

Cis,trans isomers

Isomers with the same connectivity but a different arrangement of atoms in space because of a ring or carbon-carbon double bond

Methylene

The alkenyl group CH2=

Vinyl

The alkenyl group CH2=CH—

Allyl

The alkenyl group CH2=CHCH2—

Z

Configuration in which groups of higher priority are on the same side of a carbon-carbon double bond

E

Configuration in which groups of higher priority are on opposite sides of a carbon-carbon double bond

Index of Hydrogen Deficiency (IHD)

(Hreference - Hmolecule)/2

Addition reaction

A reaction in which two atoms or ions react with a double bond, forming a compound with the two new groups bonded to the original double-bonded carbons

Reactive intermediate

A species corresponding to an energy minimum between two transition states

Rate-determining step

The step in a reaction that crosses the highest energy barrier

Bond dissociation enthalpy (BDE)

The energy required to break a bond into two radicals in the gas phase at 25°C

Markovnikov's rule

When HX, H2O, or ROH adds to an alkene, hydrogen adds to the double-bond carbon with more hydrogens

Inductive effect

The polarization of electrons from adjacent sigma bonds toward an electron-deficient atom

Hydration

The addition of water to an alkene

Oxonium ion

An ion formed when water bonds to a carbocation and the oxygen has a positive charge

Rearrangement

A change in the connectivity of atoms in a product compared with the starting material

1,2 shift

Movement of an atom or group of atoms with its bonding electrons from one atom to an adjacent electron-deficient atom

Stereoselective reaction

A reaction in which one stereoisomer forms preferentially over the others

Anti stereoselectivity

Addition of atoms or groups of atoms to opposite faces of a carbon-carbon double bond

Halohydrin

A compound containing a halogen atom and a hydroxyl group on adjacent carbons

Oxymercuration

A reaction that adds water to an alkene using a mercury-containing intermediate

Reduction

Gain of electrons, or gain of hydrogen, loss of oxygen, or both

Syn stereoselective

Addition in which the reacting groups add to the same face of a carbon-carbon double bond

Oxidation

Loss of electrons, or loss of hydrogen, gain of oxygen, or both

Glycol

A compound containing hydroxyl groups on adjacent carbons

Vicinal diol

A compound containing hydroxyl groups on adjacent carbons

Stereospecific reaction

A reaction in which the stereochemistry of the product depends on the stereochemistry of the starting material

Brønsted-Lowry acid?

A proton donor

Brønsted-Lowry base?

A proton acceptor

How do you identify the conjugate base of an acid?

Remove a proton from the acid

How do you identify the conjugate acid of a base?

Add a proton to the base

Carbocation

A species in which carbon has only six valence-shell electrons and a positive charge

What does a small pKa value indicate?

A stronger acid

What does a large pKa value indicate?

A weaker acid

What does ΔG‡ control?

The rate of a reaction

What is a diene?

A compound containing two carbon-carbon double bonds

What is a triene?

A compound containing three carbon-carbon double bonds

What is a polyene?

A compound containing several carbon-carbon double bonds

What is a racemic mixture?

A 1:1 mixture of two enantiomers