reactivity at sp centres

Question 1

what is the orbital layout of sp

Answer 1

two unused p orbitals in y and z axis, 2 sp orbitals linear to each other,
sp hybrids overlap with H 1s for the sigma frame work

makes alkynes acidic due to shortened and stronger C-H bonds

Question 2

what type of base is needed to deprotonate terminal alkyne

Answer 2

base with pKa higher than 25 leaving anion and BH

eg Bu-Li+, sodium amide, sodium hyride

Question 3

what groups alkynes react with

Answer 3

acetylide anions good nucleophiles so attack primary alkyl halides, epoxides and carbonyl groups

Question 4

how are alkyns hydrated

Answer 4

at high temperature with H2O and H2SO4 270*c

using gold catalyst allows it to run at lower temps eg H2O, NaAUCl4 at 70*c

Question 5

how to alkyns react with dihalogens and H-halogens

Answer 5

halogens:add twice to form tetrahalides

H-halides: add twice to form geminal dihalide (halide on same C)

Question 6

how are z and E alkenes formed from alkynes

Answer 6

Z - H2 gas and lindlar catalyst

E - Na, NH3, tBuOH solvent

Question 7

what is a lindlar catalyst

Answer 7

palladium on CaCO3 poisoned with lead acetate and quinoline, the poisoning deactivates palladium so can only selectively hydrogenate alkyne but not alkene

Question 8

explain how the E alkene is formed from alkyne

Answer 8

Dissolving metal reduction
Na metal in liquid NH3 so diluted solution of solvated electrons in NH3, electron bonds onto triple the bond forming anionic carbon and a radical carbon.
anionic carbon bonds to H in tBuOH and electron from solution joins radical forming anion which then bonds to H again.