all organic synthesis pathways

Question 1

describe the 3 steps of free-radical substitution with halogens.

Answer 1

1) initiation
- produces free radical from molecules

2) propagation
- forms products & more radicals

3) termination
- removes free radicals

Question 2

under what conditions does alkanes react with halogens?

Answer 2

under UV light / on heat

Question 3

what reaction conditions are involved in the electrophilic addition of H2 to alkenes? what is the product?

Answer 3

Ni catalyst, 150C, 5 atm
forms alkanes

Question 4

what reaction conditions are involved in the electrophilic addition of steam to alkenes? what is the product?

Answer 4

conc. H3PO4 catalyst, 300-600C, 70 atm
produce alcohols

Question 5

what reaction conditions are involved in the oxidation of alkenes? what is the product?

Answer 5

acidified KMnO4 + steam
produce diols

Question 6

what are the reagents, conditions & mechanism of bromination of benzenes?

Answer 6

mechanism: electrophilic substitution
reagent: Br2
conditions: room temp. & FeBr3 catalyst

Question 7

draw the mechanism of electrophilic substitution of benzenes with bromine. *

Question 8

draw the mechanism of nitration of benzenes. *

Question 9

what are the reagents, conditions & mechanism of chlorination of benzenes?

Answer 9

mechanism: electrophilic substitution
reagent: Cl2
conditions: room temp. & FeCl3 / AlCl3 catalyst

Question 10

what are the reagents, conditions & mechanism of nitration of benzenes?

Answer 10

mechanism: electrophilic substitution
reagents: conc. HNO3 & conc. H2SO4 catalyst
conditions: below 55C

Question 11

what is the mechanism of friedel-crafts reactions?

Answer 11

electrophilic substitution

Question 12

what are the reagents and conditions of friedel-crafts alkylation?

Answer 12

reagent - RCl (chloroalkyl compound)
conditions - anhydrous AlCl3 catalyst
- heat under reflux

Question 13

draw the mechanism of friedel-crafts alkylation. *

Question 14

what are the reagents & conditions of friedel-crafts acetylation?

Answer 14

reagents - acyl chloride
conditions - anhydrous AlCl3 catalyst
- heat under reflux at 50C

Question 15

draw the mechanism of friedel-craft acetylation. *

Question 16

describe the reagents and conditions of bromination of phenols.

Answer 16

reagents - bromine water
conditions - room temp.

Question 17

draw the mechanism of bromination of phenols. *

Question 18

why does phenols not require a halogen carrier?

Answer 18

lone pair on O on -OH group is partially delocalised in the ring & activates the ring
-> higher e- density & Br2 is more polarised

Question 19

how could 2,4,6-tribromophenol be identified?

Answer 19

white solid, antiseptic smell

Question 20

how could primary amines be formed from halogenoalkanes?

Answer 20

one-step nucleophilic substitution

Question 21

how could primary amines be prepared from nitriles?

Answer 21

1- convert halogenoalkane to nitrile
reagent- ethanol & KCN
conditions - heat under reflux

2- reduce nitrile to amine
reagent- LiAlH4 in dry ether

Question 22

how are aromatic amines formed from nitroarenes?

Answer 22

reagent- Sn & HCl
conditions - heat
mechanism - reduction

Question 23

what does grignard reagents do?

Answer 23

increase carbon chain length

Question 24

how are grignard reagents made?

Answer 24

halogenoalkane dissolved in dry ether & reacted with Mg

Question 25

what does grignard reagent & methanal form?

Answer 25

primary alcohol

Question 26

what does grignard reagent & aldehyde form?

Answer 26

secondary alcohol

Question 27

what does grignard reagent & carbon dioxide form?

Answer 27

carboxylic acid

Question 28

what are the conditions and reagents of oxidation of aldehydes? what is the product?

Answer 28

carboxylic acid - heat under reflux - K2Cr2O7 & dilute H2SO4

Question 29

what compound could be tested with fehling's solution? state the conditions, reagents & observation.

Answer 29

aldehydes condition: heat gently reagents: solution with Cu2+ ions observation: Cu2+ ions reduced to CuO (red ppt) (& aldehydes oxidised to carboxylic acids)

Question 30

what compound could be tested with tollen's reagent? state the conditions, reagents & observation.

Answer 30

aldehydes condition: heat gently reagents: aq, NH3 + AgNO3 -> complex ion [Ag(NH3)2]+ observation: silver mirror forms as Ag+ (aq) reduced to Ag(s)) (& aldehydes oxidised to carboxylic acids)

Question 31

what is the reagents & conditions of reduction of carbonyls?

Answer 31

reagents: LiAlH4 in dry ether / reduction agent conditions: room temp. & Pa

Question 32

what would aldehydes & ketones be reduced to?

Answer 32

aldehyde: primary alcohols ketones: secondary alcohols

Question 33

what are formed with nucleophillic addition of carbonyls?

Answer 33

hydroxynitriles

Question 34

what are the reagents & conditions of nucleophillic addition of carbonyls? draw the mechanism.

Answer 34

reagent: HCN in presence of KCN conditions: room temp. & Pa

Question 35

what is the iodoform test specifically for?

Answer 35

carbonyls with methyl group attached next to C=O (ethanal / methyl ketones)

Question 36

what are the reagents & conditions of the iodoform test?

Answer 36

reagents - I2 with NaOH (alkali) conditions - warm gently

Question 37

what is formed in the iodoform test? state the formula and the observations.

Answer 37

CHI3, triiodomethane yellow ppt