6. Understanding Organic Reactions

Question 1

A reaction in which another atom or group of atoms replaces an atom or a group of atoms. This reaction involves σ bonds: one σ bond breaks and another is formed at the same atom.

Answer 1

Substitution Reaction

Question 2

A chemical reaction in which elements of the starting material are “lost” and a π bond is formed.

Answer 2

Elimination Reaction

Question 3

A reaction in which elements are added to a starting material. In this reaction, a π bond is broken and two σ bonds are formed.

Answer 3

Addition Reaction

Question 4

A detailed description of how bonds are broken and formed as a starting material is converted to a product.

Answer 4

Reaction Mechanism

Question 5

A reaction in which all bond forming and bond breaking occurs in one step.

Answer 5

Concerted Reaction

Question 6

A high-energy unstable intermediate formed during the conversion of a stable starting material to a stable product.

Answer 6

Reactive Intermediate

Question 7

The breaking of a covalent bond by equally dividing the electrons between the two atoms in the bond and generates uncharged radical intermediates.

Answer 7

Homolysis (Homolytic Cleavage)

Question 8

The breaking of a covalent bond by unequally dividing the electrons between the two atoms in the bond and generates charged intermediates.

Answer 8

Heterolysis (Heterloytic Cleavage)

Question 9

A half-headed curved arrow used in a reaction mechanism to denote the movement of a single electron.

Answer 9

Fishhook

Question 10

An arrow used in a reaction mechanism to denote the movement of a pair of electrons.

Answer 10

Full-Headed Curved Arrow

Question 11

A reactive intermediate with a single unpaired electron, formed by homolysis of a covalent bond.

Answer 11

Radical

Question 12

The energy absorbed or released in a reaction and is symbolized by ΔH°

Answer 12

Enthalpy Change (Heat of Reaction)

Question 13

A reaction in which the energy of the products is higher than the energy of the reactants. energy is absorbed and the ΔH° is a positive value.

Answer 13

Endothermic

Question 14

A reaction in which the energy of the products is lower than the energy of the reactants. energy is released and the ΔH° is a negative value.

Answer 14

Exothermic

Question 15

A study of the energy and equilibrium of a chemical reaction.

Answer 15

Thermodynamics

Question 16

The study of chemical reaction rates.

Answer 16

Kinetics

Question 17

A mathematical expression, denoted by the symbol Keq, which relates the amount of starting material and product at equilibrium. Keq = [products]/[starting materials].

Answer 17

Equilibrium Constant

Question 18

The free energy of a molecule and is denoted by the symbol G°.

Answer 18

Gibbs Free Energy

Question 19

The change in the amount of disorder between reactants and products in a reaction. The change is denoted by the symbol ΔS°. ΔS° = S°products − S°reactants.

Answer 19

Entropy Change

Question 20

A schematic representation of the energy changes that take place as reactants are converted to products. It indicates how readily a reaction proceeds, how many steps are involved, and how the energies of the reactants, products, and intermediates compare.

Answer 20

Energy Diagram

Question 21

The x axis in an energy diagram that represents the progress of a reaction as it proceeds from reactant to product.

Answer 21

Reaction Coordinate

Question 22

An unstable energy maximum as a chemical reaction proceeds from reactants to products. The state is at the top of an energy “hill” and can never be isolated.

Answer 22

Transition State

Question 23

symbolized by Ea, is the minimum amount of energy needed to break bonds in the reactants.

Answer 23

Energy of Activation

Question 24

In a multistep reaction mechanism, the step with the highest-energy transition state.

Answer 24

Rate-Determining Step

Question 25

An equation that shows the relationship between the rate of a reaction and the concentration of the reactants.

Answer 25

Rate Equation

Question 26

A reaction in which the concentration of both reactants affects the reaction rate and both terms appear in the rate equation. Two reactants are involved in the only step or the rate-determining step.

Answer 26

Bimolecular Reaction

Question 27

The sum of the exponents of the concentration terms in the rate equation of a reaction.

Answer 27

Order of a Rate Equation

Question 28

A rate equation in which the reaction rate depends on the concentration of two reactants.

Answer 28

Second-Order Rate Equation

Question 29

A reaction that has only one reactant involved in the rate-determining step, so the concentration of only one reactant appears in the rate equation.

Answer 29

Unimolecular Reaction

Question 30

A rate equation in which the reaction rate depends on the concentration of only one reactant.

Answer 30

First-Order Rate Equation

Question 31

A substance that speeds up the rate of a reaction, but is recovered unchanged at the end of the reaction and does not appear in the product.

Answer 31

Catalyst

Question 32

The region of an enzyme that binds the substrate.

Answer 32

Active Site

Question 33

An organic molecule that is transformed by the action of an enzyme.

Answer 33

Substrate

Question 34

A structure having a substrate bonded to the active site of an enzyme.

Answer 34

Enzyme-Substrate Complex