Alkynes and Their Properties

Question 1

hybridization and bond angle

Answer 1

sp hybridized

180º linear bond angle

Question 2

terminal alkyne stability

Answer 2

less stable

Question 3

internal alkyne stability

Answer 3

more stable because of hyperconjugation

Question 4

properties

Answer 4

hydrocarbon: nonpolar, hydrophobic

bonds more EN than alkenes

slightly more polar, and higher BP/MP than corresponding alkenes/alkanes

Question 5

acetylene

Answer 5

colorless gas that burns in O2 to form CO2 + H2O

releases a lot of energy: very hot flame 2800ºC

great for welding torches

Question 6

synthetic hormones

Answer 6

analogues to estradiol / progesterone but more potent

Question 7

toxic alkynes

Answer 7

poison dart frogs: histrionicotoxin

Question 8

highly flammable

Answer 8

diacetylene

in atm. of Uranus, Neptune, Pluto, moons of Saturn (Titon), and Neptune (Triton)

Question 9

terminal alkynes have an ___ proton

Answer 9

acidic b/c 50% s-char (e- held closely to nucleus)

pka 25

need strong base to remove (not NaOH/RO-)

Question 10

what strong bases can abstract terminal alkyne proton?

Answer 10

NaH sodium hydride

NaNH2 sodium amine (most frequently used)

RLi / RMgBr (organometallic R-)

Question 11

solvent to create acetylide ion

Answer 11

polar aprotic

THF, ether

USE NH3 (l) liquid ammonia