Chapter 1- alkanes

Question 0

Addition reaction

Answer 0

The reaction that occurs when two reactants add together to form a single new product with, no atoms “left over”.

Question 1

Activation energy

Answer 1

The difference in energy between ground state and transition state in a reaction. The amount of activation energy determines the rate at which the reaction proceeds. Most organic reactions have activation energies of 40—100kJ/mol.

Question 2

Anti conformation

Answer 2

The geometric arrangement around a carbon-carbon single bond in which the two largest stubstitutents are 180° apart as viewed in a Newman projection.

Question 3

Branched-chain alkane

Answer 3

An alkane that contains a branching connection of carbons as opposed to a straight-chain alkane.

Question 4

Bronsted-Lowry acid

Answer 4

A substance that donates a hydrogen ion (proton; H3O+) to a base.

Question 5

Brønsted-Lowry base

Answer 5

A substance that accepts H3O+ from an acid.

Question 6

Chain reaction

Answer 6

A reaction that, once initiated, sustains itself, in an endlessly repeating cycle of propagation steps. The radical chlorination of alkanes is an example of a chain reaction that is initiated by irradiation with light and then continues in a series of propagation steps.

Question 7

Concerted

Answer 7

A reaction that takes place in a single step without intermediates. For example, the Diels-Alder cycloaddition reaction is a concerted process.

Question 8

Condensed structure

Answer 8

A shorthand way of writing structures in which carbon-hydrogen and carbon-carbon bonds are understood rather than shown explicitly. Propane, for example, has the condensed structure CH3CH2CH3.

Question 9

Conformation

Answer 9

The three-dimensional shape of a molecule at any given instant, assuming that rotation around single bonds is frozen.

Question 10

Conformer

Answer 10

A conformational isomer.

Question 11

Conjugate acid

Answer 11

The product that results from protonation of a Bronsted-Lowry base.

Question 12

Conjugate base

Answer 12

The anion that results from deprotonation of a Bronsted-Lowry acid.

Question 13

Constitutional isomers

Answer 13

Isomers that have their atoms connected in a different order. For example, butane and 2-methylpropane are constitutional isomers.

Question 14

Degree of unstauration

Answer 14

The number of rings and/or multiple bonds in a molecule.

Question 15

Eclipsed confirmation

Answer 15

The geometric arrangement around a carbon-carbon single bond in which the bonds to substituents on one carbon are parallel to the bonds to substituents on the neighboring carbon as viewed in a Newman projection.

Question 16

Eclipsing strain

Answer 16

The strain energy in a molecule caused by electron repulsions between eclipsed bonds. Eclipsing strain is also called torsional strain.

Question 17

Elimination reaction

Answer 17

What occurs when a single reactant splits into two products.

Question 18

Endothermic

Answer 18

A reaction that absorbs heat and therefore has a positive enthalpy change.

Question 19

Enthalpy change, ΔH

Answer 19

The heat of reaction. The enthalpy change that occurs during a reaction is a measure of the difference in total bond energy between reactants and products.

Question 20

Entropy change, ΔS

Answer 20

The change in amount of disorder. The entropy change that occurs during a reaction is a measure of the difference in disorder between reactants and products.

Question 21

Enzyme

Answer 21

A biological catalyst. Enzymes are large proteins that catalyze specific biochemical reactions.

Question 22

Intermediate

Answer 22

A species that is formed during the course of a multistep reaction but is not the final product. Intermediates are more stable than transition states, but may or may not be stable enough to isolate.

Question 23

Isomers

Answer 23

Compounds that have the same molecular formula but different structures

Question 24

Kinetics

Answer 24

Referring to reaction rates. Kinetic measurements are useful for helping to determine
reaction mechanisms.

Question 25

Lewis acid

Answer 25

A substance with a vacant low-energy orbital that can accept an electron pair from a base. All electrophiles are Lewis acids.

Question 26

Lewis base

Answer 26

A substance that donates an electron lone pair to an acid. All nucleophiles are Lewis bases.

Question 27

Lewis structure

Answer 27

A representation of a molecule showing valence electrons as dots.

Question 28

Line-bond structure

Answer 28

A representation of a molecule showing valence electrons as dots.

Question 29

Lone-pair electrons

Answer 29

Nonbonding valence-shell electron pairs. Lone-pair electrons are used by nucleophiles in their reactions with electrophiles.

Question 30

Mechanism

Answer 30

A complete description of how a reaction occurs. A mechanism must account for all starting materials and all products, and must describe the details of each individual step in the overall reaction process.

Question 31

Methylene group

Answer 31

A-CH2-or = CH2 group.

Question 32

Newman projection

Answer 32

A means of indicating stereochemical relationships between substituent groups on neighboring carbons. The carbon-carbon bond is viewed end-on, and the carbons are indicated by a circle. Bonds radiating from the center of the circle are attached to the front carbon, and bonds radiating from the edge of the circle are attached to the rear carbon.

Question 33

Normal alkane

Answer 33

A straight-chain alkane, as opposed to a branched alkane. Normal alkanes are denoted by the suffix n, as in n-C4H10 (n-butane)

Question 34

Radical

Answer 34

A species that has an odd number of electrons, such as the chlorine radical, Cl·

Question 35

Radical reaction

Answer 35

A reaction in which bonds are made by donation of one electron from each of two reactants and in which bonds are broken when each fragment leaves with one electron.

Question 36

Reaction every diagram

Answer 36

A representation of the course of a reaction, in which free energy is plotted as a function of reaction progress. Reactants, transition states, intermediates, and products are represented, and their appropriate energy levels are indicated.

Question 37

Rearrangement reaction

Answer 37

What occurs when a single reactant undergoes a reorganization of bonds and atoms to yield an isomeric product.

Question 38

Reduction

Answer 38

A reaction that causes an increase of electron ownership by carbon, either by bond breaking between carbon and a more electronegative atom or by bond formation between carbon and a less electronegative atom.

Question 39

Sawhorse structure

Answer 39

A manner of representing stereochemistry that uses a stick drawing and gives a perspective view of the conformation around a single bond.

Question 40

Skeletal structure

Answer 40

A shorthand way of writing structures in which carbon atoms are assumed to be at each intersection of two lines (bonds) and at the end of each line.

Question 41

Sp orbital

Answer 41

A hybrid orbital derived from the combination of an s and a p atomic orbital. The two sp orbitals that result from hybridization are oriented at an angle of 180° to each other.

Question 42

Sp2 orbital

Answer 42

A hybrid orbital derived by combination of an s atomic orbital with two p atomic orbitals. The three sp2 hybrid orbitals that result lie in a plane at angles of 120° to each other.

Question 43

Sp3 orbital

Answer 43

A hybrid orbital derived by combination of an s atomic orbital with three p atomic orbitals. The four sp3 hybrid orbitals that result are directed toward the corners of a regular tetrahedron at angles of 109° to each other.

Question 44

Staggered confirmation

Answer 44

The three dimensional arrangement of atoms around a carbon-carbon single bond in which the bonds on one carbon bisect the bond angles on the second carbon as viewed end-on.

Question 45

Straight-chain alkane

Answer 45

An alkane whose carbon atoms are connected without branching.

Question 46

Thermodynamic control

Answer 46

An equilibrium reaction that yields the lowest-energy, most stable product is said to be thermodynamically controlled.

Question 47

Torsional strain

Answer 47

The strain in a molecule caused by electron repulsion between eclipsed bonds. Torsional strain is also called eclipsing strain

Question 48

Transition state

Answer 48

An activated complex between reactants, representing the highest energy point on a reaction curve. Transition states are unstable complexes that can’t be isolated.

Question 49

Valence bond theory

Answer 49

A bonding theory that describes a covalent bond as resulting from the overlap of two atomic orbitals.