Chem 261 Middy Two

1,2 dihydroxylation

process using either osmium tetroxide or KMnO4 to break alkene DBs and synthesize 1,2-diols

bond is broken and OH groups are added

osmium tetroxide and formation of 1,2-diols

1. alkene and osmium tetroxide → DBs cleaved to form osmate ester
2. osmate ester + H2S or NaHSO3 → 1,2-diol via syn addition of two OH

epoxide

cyclic ether with three membered ring

O-C-C but cyclic

dehydration of alcohols (preparation of alkenes)

heat with Al2O3 at 450 degrees

90% yield of alkene

dehydrohalogenation

E1 elimination

in RDS, I type of molecule is undergoing change in covalency

E2 elimination

In RDS, 2 types of molecules are undergoing changes in covalence

strong base in E2

bulkier so choose more accessible bond to be broken

more likely to result in zaitzev

zaitsev’s rule

a small base (like ethoxide or hydroxide) favours highly substituted alkene product (more stable)

alkyne hybridization

4sp bonds and two pi bonds

double and triple bonds in a structure

\-enynes

alkyne chemical properties

H bonded to C of terminal alkyne is more acidic than H bonded to C in alkane or alkene

hydrogenation

H2,Pd/CaCO3 and lindlar’s catalyst to cleave alkyne into alkene

vicinal dihalide

halogens on adjacent carbons