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Flashcards in Mechanisms Deck (14):
1

Hydroboration-oxidation (BH3)

stereo- Syn

OH(takes place of B)- anti-markovnikov

-concerted transition state

-oxidation (NaOH/H2O2)= removal of Br and replace with OH

2

Hydrogenation (catalytic) (H2)

Stereo-Syn

Regio- doesn't matter b/c adding same thing to both sides

3

Hydration (acid catalyzed)

H3O converts to water which breaks double bond, forming carbocation. Water bonds to carbocation. Another water comes and steals H creating OH.

Stereo- both syn and anti

Regio- OH= markovnikov

4

Halogenation (Br2, etc.)

Forms bromonium ion from double bond. Other bromine attacks from backside to break triangle.

Stereo- anti

Regio- First Br= anti-markovnikov

5

Oxymercuration-reduction

Stereo- anti

Regio- Hg(later H) = anti-markovnikov

6

HBr addition (no solvent)

stero- both syn and anti

regio- Br = markovnikove

carbocation mechanism

7

HBr (in peroxides- Free-radical addition)

stereo- both syn and anti

regio- Br = anti- markovnikov

-peroxide forms radicals, steals H from Hbr which makes Br radical

-Br radical attacks double bond, going less substituted

-Free radical carbo cation steals H from another HBr

8

Ozonolysis

-Ozone attacks double bond forming malozonide (3 Os on top)

-malozonide rearranges (starts at c-c bond) to ozonide (2 top, 1 below)

- Malozonide with Me2S (DMS) gives normal products (DMS taking one oxygen to become DMSO)

-Malozonide with (H2O2/H2O) forms carboxylic acids by replacing H with OH

9

Halohydrin formation (Br2 in H2O)

stereo- anti

regio- OH= markovnikov

Water backside attacks the bromonium ion, taking the spot that to other Br would have gone (but markovnikov)

10

Formation of grignard reagents

- Mg Switches places with a halogen attached to an alkyl group so that the order is: alkyl group--mg--halogen

11

Formation of Organolithium

Li displaces a halogen attached to an alkyl group so that you end up with: R-Li and Li-halogen

12

Reactions with organometallic

Alkyl group steals H from water, Mg-halogen group or Li left with + charge, OH- left.

13

H+ reaction

-Will react like acid/base reaction

-can cause carbocation shifts

14

Free radical halogenation (in presence of light/heat)

-light split Cl2, forming radicals

-Cl radical attacks H on H-R, forming R radical

-R radical attacks another Cl2

-Two Cl radicals recombine to end cycle