O5: Reactive intermidiates

What does a Tin hydride reduction rxn do?

state reagents

It is a type of radical chain rxn that remove the functional group,

eg. R-Br → R-H

“AIBN”and “Bu3SnH”

Show the full rxn of turning

R-Br → R-H

Showing the mechanisms and naming the steps

draw AIBN

write a Barton-McCombie Dehydroxylation via Xanthates including type of alcohols and reagents , draw xanathate formation

alcohols included for formation 2nd and 3rd alcohols

for breaking 2nd and 3rd with O-FG

Draw a xanthate removal

Talk about EWG and EDG and their effect on radical alkene rxn

Give examples of EWG and EDG and how do you personally tell them apart

EWG have bond with a C or another atom next to an electronegative atom , and Halogens

While EDG have an atom bond next to eg, H, or a lower electronegative group, or a phenyl

• EWGs: -NO2, -CN, -COOH, -CHO, -CF3, halogens

• EDGs: -OH, -NH2, -OR, -CH3, -C6H5 (phenyl in some contexts)

What slows down radical rxns state 4 things

More stable radicals = slower rxn

Conjugation is stablising = more conjugation slower rxn

EDG stabilise by hyperconjugation = slower rxn

EDG faster rxn by induction, but if they allow reasonance then slower rxn

Sterics: bulky groups stabilise radicals while smaller make rxn faster

What radicals have fastest rxn ( primary, secondary,……) and why

Primary radicals (Fastest)>2> 3

Due to primary having the highest bond dissociation Energy ( lower BDE means Higher stability)

Show the mechanism behind the polymer effect

Draw the mechanism if you add heat to this

What is the favoured path for molecules rxn with e- with EWG, what would change if the group was OMe for example

the double bond on the left will bond to the e-, causing negative on ortho left and radical on meta right then takes proton

Give reagents and products to forming the OX, and give the mech to getting RH

draw rxn mech and product, and how could we get rid of the OX to form another product (reagents only)

What reagents should you use for this intermolecular addition, show mechanism as well

HSnBu3 and AIBN

write out eg. of a radical clockwise of R - H

turns RH to ROH

use P450, draw mech and products that formed and not formed

Do the same for this

Using this do a Pinacol coupling rxn

notice 1 O up and the other is down

Give reagent and mech for this Carbonyl-Alkene Coupling Reactions

Orbital wise draw a singlet and a triplet carbene describe each of the e-s, how would triplet carbene bond to 2Cp

What stabilises the empty p orbital of a singlet

Triplet carbene will use one for sigma bonding to Cp as X

and the other one bonding with a pi bonding, a Cp as L2X

EWG pi interactions such with halogen stabilises the empty p orbital of a singlet

what R groups are prefered for each of the carbenes,and what can stabilie singlet carbenes

Show mechanism drawing the full product for the Generation from tosylhydrazones

From the the Bamford-Stevens Reaction show how can you isolate this diazo compound and show how it will react in protic vs aprotic to give E alkenes

Show missing reagents and mechanism to making these carbenes

How would singlet carbene react with E and Z alkene, what would triplet show differently and why draw example

Turn this to a zinc carbenoid show reagents and product

Draw products of these Simmons-Smith reactions

Draw product with stereohemistry and why?

Draw product with stereohemistry (Why?) of a Simmons-Smith reactions

Show the mech of this singlet carbene rxn

Show the mech of this tripletrcarbene rxn

Show a carbene rearrangement reaction

can stick H, aryl, alkyls,…

Show mech and product

double bond NNHTs, breaks to become carbene ( remember)

Show wolf rearegement of this

Continue the rxn using wolff rearengement

Show missing products and their mech