Organic 4: Alcohols & Alkyl Halides

Question 1

Functional group

Answer 1

atom or group in a molecule most responsible for the reaction the compound undergoes under a prescribed set of conditions

Question 2

Mechanism

Answer 2

how the structure of the reactant is transformed to that of the product

Question 3

Alcohols

Answer 3

compound of the type R-OH

Question 4

Alkyl halides

Answer 4

compound of the type RX, in which X is a halogen substituent (F, Cl, Br, I)

Question 5

R

Answer 5

stands for an alkyl group

Question 6

Functional class nomenclature

Answer 6

alkyl group & halide are designated as separate words; alkyl group named on the basis of its longest continuous chain beginning at the carbon to which the halogen is attached; alkyl + halide

Question 7

Substitutive nomenclature

Answer 7

treats the halogen as a halo substituent on an alkane chain; carbon chain numbered in the direction that gives the substituted carbon the lower number; locants required

Question 8

Induced-dipole/induced-dipole forces

Answer 8

the only intermolecular attractive forces available to nonpolar molecules such as alkanes and are important in polar molecules as well

Question 9

Dipole-dipole attractive force

Answer 9

2 molecules of a polar substance experience a mutual attraction between the positively polarized region of one molecule and the negatively polarized region of the other

Question 10

Dipole/induced-dipole force

Answer 10

combines features of both the induced-dipole/induced-dipole & dipole-dipole attractive forces; a polar region of 1 molecule alters the electron distribution in a nonpolar region of another in a direction that produces an attractive force between them

Question 11

Hydrogen bonding

Answer 11

type of dipole-dipole attractive force in which a positively polarized hydrogen of 1 molecule is weakly bonded to a negatively polarized atom of an adjacent molecule; typically involves the hydrogen of one -OH or -NH group and the oxygen or nitrogen of another

Question 12

Polarizability

Answer 12

induced-dipole/induced-dipole attractions are favored when the electron cloud around an atom is easily distorted; more pronounced when the electrons are farther from the nucleus than when they are closer

Question 13

Substitution

Answer 13

reaction of an alcohol with a hydrogen halide; a halogen, usually Cl or Br, replaces a hydroxyl group as a substituent on carbon

Question 14

Mechanism

Answer 14

step-by-step pathway of bond cleavage and bond formation that leads from reactants to products

Question 15

Elementary step

Answer 15

a step in a reaction that involves only one transition state

Question 16

Concerted reaction

Answer 16

reaction that occurs in a single elementary step

Question 17

Alkyloxonium ion (ROH2+)

Answer 17

proton transfer to an alcohol results in this

Question 18

Molecularity

Answer 18

the number of species that react together in the same elementary step of a reaction mechanism

Question 19

Bimolecular

Answer 19

a process by which 2 particles react in the same elementary step

Question 20

Intermediate

Answer 20

transient species formed during a chemical reaction; typically, it is not stable under the conditions of its formation and proceeds further to form the product; unlike a transition state, which corresponds to a maximum along a potential energy surface, this lies at a potential energy minimum

Question 21

Potential energy diagram

Answer 21

plot of potential energy versus some arbitrary measure of the degree to which a reaction has proceeded (the reaction coordinate); the point of maximum potential energy is the transition state

Question 22

Transition state

Answer 22

point of maximum potential energy encountered by the reactants as they proceed to products

Question 23

Hammond’s Postulate

Answer 23

if 2 states are similar in energy, they are similar in structure

Question 24

Carbocation

Answer 24

an ion that contains a positively charged carbon

Question 25

Unimolecular

Answer 25

describing a step in a reaction mechanism in which only 1 particle undergoes a chemical change at the transition state

Question 26

Electrophilic

Answer 26

electron-loving or electron-seeking; Lewis acids (electron-pair acceptors)

Question 27

Nucleophiles

Answer 27

Lewis bases that react with electrophiles; “nucleus seekers”; have an unshared electron pair they can use in covalent bond formation

Question 28

Rate-determining step

Answer 28

slowest step in a reaction; a reaction can proceed no faster than its slowest step

Question 29

SN1 Mechanism

Answer 29

Substitutive nucleophilic unimolecular mechanism; mechanism for nucleophilic substitution characterized by a 2-step process; the 1st step is rate-determining and is the ionization of an alkyl halide to a carbocation and a halide ion

Question 30

Hyperconjugation

Answer 30

delocalization of electrons in a sigma bond through a system of overlapping orbitals

Question 31

SN2 Mechanism

Answer 31

nucleophilic substitutions that have a bimolecular rate-determining step

Question 32

Kinetics

Answer 32

study of the rates of chemical reactions and the factors that influence reaction rate

Question 33

Halogenation

Answer 33

replacement of a hydrogen by a halogen; the most frequently encountered examples are the free-radical ________ of alkanes and the ________ of arenes by electrophilic aromatic substitution

Question 34

Free Radicals

Answer 34

species that contain unpaired electrons

Question 35

Spin density

Answer 35

measure of unpaired electron density at a particular point in a molecule (tells us where the unpaired electron is most likely to be)

Question 36

Homolytic cleavage

Answer 36

bond between 2 atoms is broken so that each of them retains one of the electrons in the bond

Question 37

Heterolytic cleavage

Answer 37

bond between 2 atoms is broken, but one fragment retains both electrons

Question 38

Bond dissociation enthalpy (D)

Answer 38

energy required for homolytic bond cleavage

Question 39

Endothermic

Answer 39

a positive value for heats of reaction signifies this type of reaction, where the reactants are more stable than the products

Question 40

Initiation step

Answer 40

a process which causes a reaction, usually a free-radical reaction, to begin but which by itself is not the principal source of products; the ___ ___ in the halogenation of an alkane is the dissociation of a halogen molecule to 2 halogen atoms

Question 41

Propagation steps

Answer 41

elementary steps that repeat over and over again in a chain reaction; almost all of the products in a chain reaction arise from these

Question 42

Chain reaction

Answer 42

reaction mechanism in which a sequence of individual steps repeats itself many times, usually because a reactive intermediate consumed in 1 step is regenerated in a subsequent step; the halogenation of alkanes is a chain reaction proceeding via free-radical intermediates

Question 43

Chain-terminating steps

Answer 43

a chemical reaction that stops further growth of a polymer chain

Question 44

Photochemical reactions

Answer 44

reactions that occur when light energy is absorbed by a molecule