Key mechanisms of organic

Question 1

show how imines have resonance forms that deduces reactivity

Answer 1

imine lone pair pushed to alpha carbon, making alpha carbon nucleophilic, which attacks electrophile

Question 2

draw mechanism for nitration of benzene, what type of reaction is this?

Answer 2

electrophilic aromatic substitution
electrophile is NO2+
check mechanism

Question 3

how do substituents effect EAS?

Answer 3

will effect rate and selectivity of EAS,
EWGs make benzene less nucleophilic so slower EAS,
EDGs make benzene more nucleophilic so faster reaction

Question 4

Draw mechanism of EAS of pydridine with N-Oxides and NO2 group
(3steps)

Answer 4

protection with mCBPA, EAS, deprotection with PPh3
check notes

Question 5

What is Vilsmier-Haak reaction used for?
draw mechanism (3)

Answer 5

used for over reactive heteroatomics,
1-formation of electrophile (DMF+POCL3)
2-EAS
3-hydrolysis of imine

Question 6

What are indoles? explain their reactivity

Answer 6

reactive pyrrole ring attached to unreactive benzene ring,
pyrrole will undergo EAS but on 3 position so benzenes aromaticity is not disturbed

Question 7

Draw mechanism for addition elimination reaction of 1-floro,4-nitrobenzene

Answer 7

N lone pair attacks electrophilic carbon on C-F
NO2 stabilises intermediate and helps kick out F.

Question 8

Draw chichibabin reaction, formation of 2-aminopyridine,
What type of reaction is this?

Answer 8

nucleophilic aromatic substitution on pyridine,

Question 9

Whats the equation used to find A values?

Answer 9

A+-RTln(K)
K=equilibrium constant
K=e^(-A/RT)

Question 10

draw mechanism of irreversible cyclisation of ketone
what are some general rules?
what does the rate depend on?

Answer 10

base causes ketone to form enolate, enolate carbon attacks end carbon forming ring
-Sn2 like reaction
-nucleophile must be able to reach carbon-LG antibonding orbital for closure to work
-Ring closure rate depends on size of ring formed 3>5>6»4

Question 11

Draw cyclisation of help2-6dienone.
what type of reaction is this? what reagents needed?

Answer 11

reagents-NaOEt, EtOH
Robinson annulation, E1CB elimination as enolate formed as cb of ketone

Question 12

Draw mechanism of formation of cyclopropane from singlet carbene and alkene

Answer 12

singlet carbene generated from CCl3H, carbenes are electrophilic so prefer to react with electron rich alkenes

Question 13

describe pyridines reactivity

Answer 13

al 5 carbons and the nitrogen is sp2 hybridized
the lone pair on nitrogen is orthogonal to the ring so are not involved in the pi system.
electronegative nitrogen pulls electron density towards itself making the pi system electron poor, so will not undergo any EAS unless activated by N-Oxides

Question 14

in the Peterson olefination, which conditions result in which isomer?

Answer 14

with basic conditions, the Z isomer is formed, consider mechanism with rotation,
with acidic conditions, E isomer formed

Question 15

What is the Wittig reaction used for?
How can we get selectivity? draw mech

Answer 15

Wittig reaction used to convert aldehydes/ ketones into alkenes.
done via formation of phosphonium ylide and 2+2 cycloaddition .
we et selectivity by using a stabilised ylide for E isomers and destabilised ylides for Z isomers

Question 16

Draw mechanism of epoxide formation from cyclohexanone

Answer 16

sulfonium ylide attacks carbonyl carbon forming O anion, negative charge on O pushes out sulphur group.

Question 17

What is ambident reactivity?

Answer 17

means theres two electrophilic sites at two alternate and strongly reactive centres.
causing the option for 1,2 or 1,4 addition