ch 9 organic chemistry

what makes alkynes reactive

two pi bonds → electron rich → undergo addition reaction

how are alkynes formed from dihalides?

double elimination using a strong base removes 2 HX → forms triple bond

what type of halides form alkynes via elimination

Vinylic dihalides with strong bases

what type of reactions fo alynes undergo?

electrophilic addition reaction

why are vinylic carbocations unstable

positive charge is on sp carbon (less stabilizes, only one r group)

what happens when HX is added to an alkyne

forms vinyl halide → then dihalide (markovnikov addition)

what happens when X₂ (Br/Cl) is added

forms dihaloalkene → tetrahalide

product of Hg²⁺ - catalyzed hydration?

ketone

what is tautomerization

conversion of enol (C=C-OH) → ketone (C=O)

product for terminal alkynes

aldehyde (anti-markonikov)

product of internal alkynes

ketone

what does H₂ + Pd/C do

fully reduces → alkane

what does lindar catalyst do

partial reduction → cis-alkene

what does Li/NH₃ do?

partial reduction → trans-alkene

what happens during oxidative cleavage

triple bond breaks → forms carboxylic acids or CO₂

what forms when a terminal alkyne is deprotonated

acetylide anion (alkyne w a negative charge on side)

what do acetylide anions do

act as strong nucelophiles and bases

what reaction forms a longer carbocation chain

alkylation of acetylide anion (SN2)

what is the limitation of acetylide alkylation

only works with primary alkyl halides (second and third → elimination)

most stable anion

acetylide anion le

least stable anion

alkyl anion