Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Year 1 Organic Chemistry > Topic 15: Synthesis of Complex Aromatic Molecules > Flashcards

Topic 15: Synthesis of Complex Aromatic Molecules Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Chemistry flashcards Periodic Table flashcards Chemistry 101 flashcards Organic Chemistry 101 flashcards
1
Q

Methods of adding carbon substituents to benzene

A

Gringard reagents (can make benzylic groups with alcohols + other alkyl groups
Carbonyl reduction reactions e.g. Freidel Crafts Acylation
Oxidation at benzylic position

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Formation of the Gringard reagent C6H5MgBr (phenyl-magnesium bromide)
2 steps

A

Halogenation of benzene with Br2 and FeBr3
to form C6H5Br
This reacts with Mg, Et2O to form C6H5MgBr

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

C6H5MgBr reaction with epoxide

A

C-Mg bond attacks unsubstituted C
Reacts with acid (H3O^+) to form a benzyl alcohol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

C6H5MgBr reaction with aldehyde

A

C-Mg bond attacks electrophilic C
curly arrow from C=O bond to O
Reacts with acid (H3O^+) to form a benzyl alcohol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

C6H5MgBr reaction with R-C-X

A

Forms C6H5-C-R
A way to add alkyl groups without scrambling occuring like in Freidel Crafts alkylation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Reaction of ketone formed by … with H2HNH2 under presence of a … and … forms a … where 2 … replace the C=O. This is called a … . The same product can be formed from the same starting material via the … .It reacts with … under the presence of … . Or, by reacting it with a …, … and … .The C=O is replaced with … forming a … structure. This then reacts via … with … and a … catalyst. These methods have … than Freidel Crafts alkylation

A

acylation
base
heat
alkyl benzene
Hs
Wolf Kishner reduction
Clemmensen reduction
Zn/HG amalgam
HCl
dithiol (HS-R-HS)
BF3
OEt
2 C-S bonds
ring
reduction
H2
Raney-Nickel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Unusual reaction can occur on the benzylic carbon in the structure C6H5CH2R because … . e.g. … carried out by … using … as a solvent as … is a good oxidising agent. This forms a … .Oxidation to … can also occur using the starting material … where R = … .It reacts with … under … . Bromination to alkyl halide (C6H5CH3) can also occur using … under the conditions … or … to form … .The reagent … is … and forms a … which reacts with the starting material

A

reactive intermediates are stabilised by resonance around the ring
oxidation to aldehydes/ketones
IDX (2-iodoxybenzoic acid)
DMSO/Ph-F
iodine (v)
aldehyde or ketone
carboxylic acids
C6H5R
CH3, CH2R, CHR2
KMnO4 / Na2Cr2O4, H2SO4
heat
NBS
heat
hv
C6H5CH2Br
NBS
stabilised by resonance
Br radical

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Aniline is a useful … as it acts as a precursor to … .It is formed by reacting … with … and … to form … .It was then … to … using either … or …

A

synthen
amides and diazo
benzene
H2SO4
HNO3
C6H5NO2 (nitrobenzene)
reduced
C6H5NH2 (aniline)
Sn, HCl
H2 , Pd/C catalyst

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Aniline can react with either … or … to form amides

A

acetic anhydride (Me-C(=O)-O-C(=O)-Me)
acetyl chloride (Me-C(=O)-Cl)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

The diazoisation of aniline occurs by reacting it with … under … conditions to form … .First, the … reacts with … to form … .2 of these molecules react together. A curly arrow goes from … to … and from … to … to form … and … under … . The … product reacts with aniline. A curly arrow goes from … to … and from … to … to form … .This can react under … to form … .A curly arrow goes from … to … and from … to … to form … under … to form … .A curly arrow goes from … to … and from … to … to form … which forms a salt with …

A

NaNO2, HCl
0-5 degrees celsius
benzenediazonium cation (C6H5-N^+(triple bond)N-Cl^-
NaNO2
HCl
H-O-N=O
lone pair on the O (double bonded to N, first molecule)
the H on the 2nd molecule
the H-O bond on the 2nd molecule
the O (bonded to H and N, second molecule)
H-O-N=O^+-H
O^–N=O
equilibrium
electrophilic (H-O-N=O^+-H)
N lone pair on aniline
N on H-O-N=O^+-H
The N=O^+ double bond
O^+
C6H5-NH2-N(OH)2
equilibrium (+/- H^+)
C6H5-NH-N(-OH)-H2O^+
lone pair on N (attached to C and H)
N-N bond
N-O^+ bond
H
C6H5-N^+(-H)=N-OH
equilibrium (-/+ H^+)
C6H5-N=N-O^+H2
Lone pair on N (attached to ring)
N=N bond
N-O^+ bond
H
C6H5-N6+(triple bond)N
Cl^-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

C6H5-N6+(triple bond)N can react with … to form C6H5X, … to form C6H5I, … to form phenol (C6H5OH), … to form benzene or … to form C6H5CN

A

CuX
KI
water, heat
H3PO2 (hypo phosphorus acid)
CuCN, heat

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

OH, OR, SR, NHR, NR2, NHC(O)
framework
activating/deactivating
directing effect

A

pi
very activating (+M)
ortho/para (extra resonance structure)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

alkyl, aromatic
framework
activating/deactivating
directing effect

A

sigma
activating (+I)
ortho/para (+I hyper conjugation)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

NO2, SO3H, CHO, COR, CO2R, CONR2, CN
framework
activating/deactivating
directing effect

A

pi
very deactivating (-M)
meta

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

CF3, NR3^+, NH3^+
framework
activating/deactivating
directing effect

A

sigma
deactivating (-I)
meta

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

F, Cl, Br, I
framework
activating/deactivating
directing effect

A

pi (responsible for regioselectivity) and sigma (deactivating)
deactivating (-I)
ortho/para (extra resonance structure)

17
Q

Expected ratio of ortho : para when adding electrophile to C6H5R

A

1:2

18
Q

How to favour para over ortho
(2 methods)

A

Use larger group such as tertiary butyl as the steric block the ortho position .
Make a smaller group larger e.g. reacting Br2 with phenol at room temp would form COH-CBr-CH-CBr-CH-CBr ring (no catalyst as phenol very activating). Make OH group larger by reacting with acid anhydride/chloride to form ester which blocks ortho position + make less activating compound. React with Br2 at 0 degrees celsius to avoid polysubstitution. React with H2O, H^+ (equilibrium) to form alcohol from ester

19
Q

How to favour ortho over para

A

Use sulfonation as its reversible
React phenol with oleum (H2SO4, SO3) at 100 degrees celsius (reversible reaction) to form phenol ring with SO3H at ortho and para position (1,3 substitution), makes less activating. Treat with NaOH to deprotonate SO3H groups then Br2 as both SO3^- groups direct meta. Can remove SO3 groups at 200 degrees celsius by steam distillation (reversible reaction) with H2O and H2SO4 to form 2-bromophenol

20
Q

trend for halogens, NH2, NO2, alkyl, CF3 in terms of how activating they are to benzene ring

A

NH2 > alkyl > halogen > CF3 > NO2

21
Q

What dictates the regioselectivity ?

A

Regioselectivity is a kinetic effect
Stability of Wheland intermediate

22
Q

Hammond postulate

A

The TS structure will resemble the closest structure to it in energy

23
Q

Groups with no lone pairs (e.g. alkyl groups) direct … due to … .The Wheland intermediate is a … with the initial … on the … and … double bonds. The … is stabilised by … and both variations of the intermediate (…) have … resonance forms

A

ortho and para (not meta)
the electron releasing affect on Wheland intermediate (+I)
carbocation
positive charge
C attached to the alkyl group
2
carbocation
hyper conjugation (+I)
ortho and para
3

24
Q

Groups with lone pairs (e.g. OH groups) direct … .The Wheland intermediate is a … with the initial … on the … and … double bonds. The … is stabilised by having … resonance forms

A

ortho and para (not meta)
carbocation
positive charge
C next to the electrophile
2
carbocation
4

25
Q

Halogens direct … even though they … .They are … through the sigma framework and direct … through the pi framwork. The … has … resonance structures for both variations

A

ortho and para (not meta)
deactivate the ring
electron withdrawing
ortho and para (not meta)
carbocation
4

26
Q

Apart from halogens (due to pi effect), all groups that deactivate the ring direct to … .This is because ..

A

the meta position
one of the carbocation resonance structures in both ortho and para have positive charge adjacent to the positive charge on the additional group causing a very destabilising effect. The meta position doesn’t have this destabilising effect.

27
Q

Ortho litigation is a … method for making … using fewer steps than … .The starting material is … and you react it with … using the solvent … which is … due to … bond. The product is … .You can react this with a … which replaces the … . The G group must contain a … and is usually a …, … or … which partake in … .The … position is activated due to the … complex that can form. It is very selective so only … products from

A

modern, convenient
1,2-disubstiuted benzene
SO3H functionalisation approach
benzene with G group attached
N-butyl lithium (BuLi)
Et2O
organometallic
Metal-C
benzene with G group and Li on ortho group
electrophile
Li
lone pair
ether
amine
amide
directed ortho metaltion
ortho
chelate
ortho

28
Q

Pd cross-coupling are … .You form … bonds between aromatic compounds

A

excellent methods to build up the functionality of aromatic compounds (make them larger)
C-C / C-N

29
Q

Buchwald-Harding coupling forms a … bond between … and … using …, … and …

A

C-N
C6H5NHR (R=alkyl/aryl)
C6H5X (X=halide)
Pd catalyst
amine
heat

30
Q

Suzuki coupling forms a … bond between … and … using … to form a …

A

C-C
C6H5X (X=halide)
C6H5B(OH)2 (phenyl moronic acid)
Pd catalyst
bis-arene (C6H5-C6H5)

31
Q

Negisho coupling forms a … bond between … and … using … to form a …

A

C-C
C6H5X (X=halide)
C6H5ZnX (X=halide)
Pd catalyst
bis-arene (C6H5-C6H5)

32
Q

Nucleopiles can attack benzene with ..
In the … position
The mechanism is not a … so there is a …

A

the right reagents and substitution pattern
ortho and para but not meta
concerted position
intermediate

33
Q

Mechanism of nucleophilic substitution of OH^- on 4-nitrochlorobenzene has 4 curly arrows: …
Forms the intermediate … slowly
The intermediate has 4 curly arrows: …
Forms … fast
This can only occur when the starting material has a good … and a good … group that is … or … to the… group

A

OH- to C attached to Cl
C=C bond next to Cl to C-C bond
C=C bond next to N^+ to C-N bond
N^+=O bond to O
6 ring carbon with 2 double bonds opposite (C2-C3, C5-C6), sp3 hybridised C1 with OH and Cl attached, C4=N^+ attached to 2 O^- (meisenheimer intermediate)
O^- to O^–N^+ bond
N^+=C4 bond to C4-C5
C5=C6 bond to C6-C1 bond
C1-Cl bond to Cl
4-nitrophenol
leaving
electron withdrawing group (usually NO2)
para
ortho
leaving

34
Q

retro synthetic analysis or retrosynthesis is a useful approach for … .You get given a … and have to work …

A

multistep organic synthesis
target molecule
backwards

Year 1 Organic Chemistry (15 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions