3. Alkynes

Question 1

how can alkynes be produced or prepared - what are the reactants involved and catalysts

Answer 1

didehydrohalogenation of dihaloalkanes

via KOH or NaOH (ethanol)

produces alkene and then alkyne

Question 2

what are the 4 types of reactions alkynes can undergo

Answer 2

hydrogenation

electrophillic addition of HX and X2

hydration

Formation of alkynide anions from terminal alkynes

Question 3

what are the bonds involved in the triple bond of a alkyne

Answer 3

1 x sigma
2 x pi

Question 4

what is the hybridization of the triple bond of alkynes

Answer 4

sp hybrid

Question 5

what is the source of e- in an alkyne reaction and what is the nucleophile

Answer 5

the triple bond is the source of e- and acts as a nucleophile

Question 6

what are the reactants involved when an alkyne produces an alkane

Answer 6

Pt/Pd catalyst

2 moles of H2

Question 7

what orientation or stereochemistry does the alkane produced from hydrogenation reaction of alkyne have

Answer 7

both H are added in syn

Question 8

what does alkyne reaction with H2 and Pt/Pd catalyst produce

Answer 8

alkane

Question 9

what are the reactants involved when an alkyne produces an E alkene

Answer 9

lithium/liquid NH3

followed by H2O

Question 10

what orientation or stereochemistry does the alkane produced from hydrogenation reaction of alkyne producing an E alkene have

Answer 10

H are added in trans

Question 11

what does alkyne reaction with 1.lithium/liquid NH3
2. H2O
produce

Answer 11

E alkene

Question 12

what are the reactants involved when an alkyne produces a Z alkene

Answer 12

[PdPb(OAc)2]/H2

lindlar catalyst

Question 13

what orientation or stereochemistry does the alkane produced from hydrogenation reaction of alkyne producing Z alkene have

Answer 13

H added in syn

Question 14

what rule does electrophillic addition of HX and H2 with alkyne follow

Answer 14

markovnikoff rule

Question 15

what happens when you add one equivalent of reagent HX or X2 to an alkyne

Answer 15

haloalkene

Question 16

what happens when you add 2 equivalents of reagent HX or X2 to an alkyne (in excess)

Answer 16

dihaloalkane

Question 17

what stereochemistry will the resulting haloalkene or dihaloalkane have from the electrophillic addition reaction of HX or X2 with alkyne

Answer 17

anti stereochemistry

Question 18

what are the reactants involved when an alkyne produces a ketone

Answer 18

1 mole equivalent of H2O with H2SO4(aq) and HqSO4

Question 19

what is produced when you add 1 mole equivalent of H2O with H2SO4(aq) and HqSO4 to an alkyne

Answer 19

produces ketones

Question 20

when an alkyne has undergone hydration reaction to form a ketone what equilibrium does it exist in - what does this mean

Answer 20

tautomeric equilibrium

internal reorganization

Question 21

what reagents and reactants are needed to produce alkynide anions from terminal alkynes

Answer 21

strong base = Na+NH2- or NaH

Question 22

what kind of alkyne can produce an alkynide anions

Answer 22

terminal alunes

Question 23

what is the structure of an alkynide anion

Answer 23

RC(triple bond)C-

Question 24

what is produced with an alkyne reacts with a strong base such as Na+NH2- or NaH

Answer 24

forms alkynide anions