Alkanes & Alkynes

Front 1

Define "electrophilic addition reaction."

Back 1

The addition of a reagent in the general form A-B by generating an electrophile during the rate determining step.

Front 2

Alkenes are saturated or unsaturated? Discuss.

Back 2

Unsaturated because the maximum number of atoms can exist with single bonds (alkanes). A saturated hydrocarbon has only single bonds.

Front 3

An electrophilic addition reaction to an alkene will produce a(n) _____.

Back 3

alkane

Front 4

Name several examples of electrophiles.

Back 4

H+, Br+, Cl+, Lewis Acids

Front 5

Formation of this kind of carbocation is favored because there is an increased ______ effect.

Back 5

Tertiary carbocation; inductive

Front 6

Halogenation of Alkenes is an example of ________. Under what conditions does halogenation occur.

Back 6

An electrophilic addition reaction which occurs instantaneously in the dark and at room temperature.

Front 7

What is unique about halogenation with bromine?

Back 7

Formation of a cyclic bromonium ion [to distribute the positive charge of the intermediate step].

Front 8

Hydration of alkenes occurs in the presence of ____ & ____ to yield _____.

Back 8

This reaction proceeds in the presence of acid (H+) catalyst and heat to give alcohols.

Front 9

In the mechanism of hydration of alkenes, what is the conjugate acid of alcohol?

Back 9

In this reaction, water is deprotonated fast to regenerate the catalyst.

Front 10

This reaction requires a finely powedered metal catalyst (e.g. Pd or Pt).

Back 10

Hydrogenation (of alkenes)

Front 11

Discuss why hydrogenation of alkenes is not an electrophilic addition.

Back 11

In this reaction, two hydrogens add to the alkene at the same time without an intermediate carbocation. Thus there is no generation of an electrophile as in electrophilic addition.

Front 12

The products of this reaction are often used to identify the specific alkene reactant.

Back 12

Ozonolysis

Front 13

An alkene which reacts with ozone will first produce a(n) ____ which is then reduced with ____ & ____ to yield _____ or ______.

Back 13

An alkene which reacts with ozone will produce an ozonide. The ozonide is then reduced with Zn & aqueous acid to yield ketones or aldehydes (carbonyl compounds).

Front 14

Discuss polymerisation of alkenes. Note one initiator.

Back 14

This reaction undergoes free-radical formation of polymers from alkene monomers. UV light or organic peroxide are initiators.

Front 15

Which of the following pairs of (alkene) geometric isomers are enantiomers? cis/trans, E/Z

Back 15

Both cis/trans & E/Z isomers are diastereomers

Front 16

True or False:
Alkenes with a Z configuration also has a cis configuration.

Back 16

Cis/trans and E/Z isomerism are unrelated and one does not indicate the other. [False]

Front 17

Dehydrogenation of alkanes is also known as _____. This mechanism requires _____.

Back 17

Elimination is the synthesis of alkenes from alkanes with heat. In losing hydrogen gas, the mechanism eliminates 2 sigma bonds to form a pi bond.

Front 18

Synthesizing an alkene from an alkyl halide requires ____ & _____. This reaction is known as _____.

Back 18

Dehydrohalogenation requires the presence of a base and heat to remove the acid from the alkyl halide.

Front 19

Name two examples of biological significance containing alkenes.

Back 19

Insect pheromones and light-mediated vision.

Front 20

Name two reactions in which two hydrogens are added to the same side in the product.
Hint: 1 alkyne reaction & 1 alkene reaction

Back 20

The hydrogenation of alkenes with metal catalyst to form alkanes and the reduction of alkynes with Lindlar's catalyst to form cis-alkenes

Front 21

Hydrogenation of an alkyne with excess hydrogen in the presence of Ni or Pt catalyst will produce _____.

Back 21

Hydrogen and alkynes in a molar ratio of (2:1) will produce alkanes.

Front 22

What is Lindlar's Catalyst and when is it used?

Back 22

A "poisoined catalyst" of deactivated palladium which is used in hydrogenation of alkynes to form cis-alkenes (not alkanes).

Front 23

Electrophilic addition follows this rule which is used to predict the product formed.

Back 23

Markovnikov's rule helps predict the alkene product of an electrophilic addition to an alkyne. [or alkane product from an alkene reaction]

Front 24

What is unique about the bromination of alkynes?

Back 24

The alkene product is mainly the trans isomer.

Front 25

This reaction requires sulfuric acid (H2SO4) and murcuric sulfate (HgSO4) catalysts.

Back 25

Hydration of alkynes.

Front 26

The hydration of alkynes produces first an unstable ____ product which will tautomerize into a(n) ______.

Back 26

Addition of water to alkynes will form enols which rearrange into more stable ketones.

Front 27

Define tautomerism.

Back 27

isomers which differ in the positions of hydrogen atoms and double bonds

Front 28

Define enol.

Back 28

an unstable alkene with a hydroxyl (OH) group attached to one of the carbons in the double bond.

Front 29

Discuss how an enol becomes a ketone.

Back 29

The proton (H) from the alcohol (OH) shifts to the neighboring carbon (in the double bond). The pi bond between the carbons is broken and reformed between the oxygen and carbon.

Front 30

These alkynes are (very) weak acids. What are the implications of this?

Back 30

Terminal aklynes can be deprotonated with strong bases.

Front 31

Terminal alkynes react with _____ and ______ (catalyst) to produce _______ which undergo _____ reaction

Back 31

Terminal alkynes reaction with NaNH2 and liquid ammonia (NH3 catalyst) to produce metal acetylide anions which undergo Sn2 nucleophilic substitution.