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FEB MOCK CHEM > Aromatic compounds, Carbonyls and Acids > Flashcards

Aromatic compounds, Carbonyls and Acids Flashcards

1
Q

what are arenes

A

compounds that contain a benzene ring in their structure

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2
Q

what is benzene’s structure

A

.six carbons atoms bonded to one hydrogen atom

.forms a ring of delocalised electrons

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3
Q

how is the delocalised ring formed

A

.outer electrons from the p-orbital of the carbons are delocalised into the centre to form the ring

.results in the formation of pi bonds

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4
Q

.what is the evidence for benzenes structure

A

.the prediction for the enthalpy change of hydrogenation was at -360 KJmol-1 but ended up being -208 Kjmol-1

.all the bond lengths between carbon atoms are the same

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5
Q

why is benzene resistant to electrophilic addition

A

.as the benzene ring is too stable to be broken down
.so it undergoes electrophilic substitution

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6
Q

how does benzene undergo electrophilic substitution

A

.the ring has a high electron density making it susceptible to attack from electrophiles

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7
Q

what is the mechanism for the electrophilic substitution for benzene

A

.draw a arrow from the central ring to the positive electrophile

.this forms a positive broken ring with the electrophile being attached
.draw an arrow form the bond between the H and C to the central ring

.this forms benzene with the electrophile attached and a hydrogen ion

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8
Q

what is halogenation

A

when benzene reacts with halogens in the presence of iron(III) bromide (FeBr3)

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9
Q

how does halogenation work

A

.the iron(III) bromide acts as the halogen carrier to polarise the bromine molecule and to form a bromine atom

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10
Q

what is nitration

A

electrophilic substitution but the electrophile is NO2+ ion

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11
Q

how is NO2+ formed for nitration

A

H2SO4 reacts with HNO3 to form H2NO3+ and HSO4-

H2NO3+ forms H2O and NO2+

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12
Q

what is the temperature needed for the nitration of one NO2+ atom

A

55C

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13
Q

what is Friedel-crafts acylation

A

.when the electron ring acts as a nucleophile
.leads to the ring attacking on acyl chlorides

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14
Q

how does Friedel-crafts work

A

.R-COCl and AlCl3 react to form R-CO+ and AlCl4-

.the R-CO is used for the reaction

.at the end the H+ removed and the AlCl4- react to form AlCl3

.the reaction forms a phenyl ketone and HCl gas

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15
Q

why does the bromine water test not work on benzene

A

.the delocalised electron density of the central ring causes benzene to be resistant to bromination

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16
Q

what are phenols

A

a benzene ring with an OH group

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17
Q

phenol with bromine water reaction

A

.phenol + 3Br2 –> 2,4,6- tribromophenol + 3HBr

.forms as a white precipitate and decolourises bromine water

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18
Q

why can phenol react with bromine water

A

the lone pair of electrons of the O is delocalised to the central ring increasing electron density and so less stable and so more susceptible to attack from electrophiles

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19
Q

nitrification of phenol

A

.reacts with dilute nitric acid to form 2-nitrophenol and 4-nitrophenol
.reacts with one NO2 group in room temperature

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20
Q

directing effects of electron donating groups (OH and NH2)

A

direct to the 2nd and 4th position

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21
Q

directing effects of electron withdrawing groups (NO2)

A

direct to the 3rd position

22
Q

what are carbonyl compounds

A

compounds containing C=O group(CO functional group)

23
Q

what does the carbonyl functional group allow to happen

A

.allows the formation of hydrogen bonds with water
.soluble in water

24
Q

what bonds do aldehydes and ketones contain

A

van der Waals only as they can not form hydrogen bond between themselves

25
Q

what is the functional group of aldehydes

A

CHO

(O=C-H)

26
Q

what is the functional group for ketones

A

C=O

27
Q

reagents used for oxidation

A

Kr2Cr2O7 and H2SO4

28
Q

why does K2Cr2O7 change from orange to green when it reacts with primary and secondary alcohol

A

when they react the K2Cr2O7 is reduced which causes the colour change

29
Q

how do you convert carbonyl compounds back into alcohols

A

.use a reducing agent (NaBH4) to undergo nucleophilic addition

.H- acts as a nucleophile

30
Q

Carbonyl to alcohol reaction

A

Ethanal + 2[H] –> Ethanol

31
Q

nucleophilic addition using HCN

A

.CN is used as the nucleophile
.carbon chain is extended by one carbon atom

32
Q

mechanism for HCN and NaBH4

A

.arrow from CN-/H- to C
.arrow from double bond to O

.CN/H bonds to the C removing a bond from the double bond
.the O is negative
.draw a arrow from the O to the H+/H from H2O for CN/H

.hydrogen bonds to the oxygen forming a alcohol

33
Q

carbonyl compound tests

A

2,4 DNP-
.when aldehydes/ketones react it forms a red precipitate
.purify the solid via recrystallisation
.find the MP of the precipitate and compare to known data to find the specific carbonyl compound

Tollens-
.reacts with aldehydes to form a silver mirror

34
Q

functional group for carboxylic acids

A

COOH

35
Q

properties of COOH

A

.forms hydrogen bonds between each other and water
.soluble in water
.higher mp/bp than alcohols/aldehydes/ketones

36
Q

carboxylic acid + base

A

salt + H2O

37
Q

carboxylic acid + metal

A

salt + H2

38
Q

carboxylic acid + metal carbonate

A

salt + CO2 + H2O

39
Q

Esters functional group

A

COO

40
Q

how to name esters

A

alcohol(YL) carboxylic acid(OATE)

41
Q

how are esters formed (esterification)

A

.carboxylic acid with alcohol in the presence of concentration sulfuric acid

.remove the OH from the acid and the H form the alcohol

42
Q

properties of ketones

A

.sweet smelling
.low bp
.good solvents

43
Q

how do acid anhydrides esterify alcohols

A

.via addition-elimination mechanism

44
Q

why is acid anhydrides used over acyl chlorides for esterfication

A

.less vigorous reaction and do not produce toxic product

45
Q

the hydrolysis of esters

A

.splits into alcohol and carboxylic acid

.needs water and either aqueous acid/alkali

46
Q

hydrolysis of esters with aqueous acid

A

forms just alcohol and carboxylic acid

47
Q

hydrolysis of esters with aqueous base

A

.forms carboxylate salt(O=C-Osalt) and alcohol

48
Q

what is the functional group for acyl chlorides

A

COCl(O=C-Cl)

oyl chloride

49
Q

what is acylation

A

when carboxylic acid reacts with SOCl2 to form acyl chlorides

50
Q

acyl chloride reactions

A

+ water = CA
+ alcohol = ester
+ ammomia = amide
+ amines = N-substituted amide

51
Q

how do acyl chlorides react

A

via nucleophilic subsitution

52
Q

acyl chloride mechanism

A

.draw acyl chloride with delta positive and negative and NH3
.arrow from lone pair on NH3 to C

.draw acyl chloride with a single bond to the O- and a bond to NH2 with a H bonded to the NH2+
.arrow from NH2-H bond to NH2
.arrow from O- to O-C bond
.arrow from C-Cl bond to Cl

. draw acyl chloride with NH2 instead of Cl and HCl

FEB MOCK CHEM (3 decks)

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