IB Chemistry on Structural Isomers and Benzene Structure

1. Class Functional group/name Suffix Examples Formula
alkane C - C ane ethane CnH2n+2
alkene C = C Alkenyl ene ethene CnH2n
alkyne C ≡ C Alkynyl yne ethyne CnH2n-2
alcohol O-H Hydroxyl ol ethanol CnH2n+1OH
ether C – O - C Ether oxyalkane methoxymethane R –O -R
ketone O
‖
C – C - C
Carbonyl one propanone CnH2nO
or
R-CO-R
aldehyde C = O
‫׀‬
H
Aldehyde anal ethanal CnH2nO
or
R -CHO
Carboxylic acid O
‖
C – O H
Carboxyl oic acid ethanoic acid CnH2n+1COOH
ester O
‖
C – O –C
Ester oate ethyl ethanoate R – COO-R
amide CONH2 Amide anamide propanamide
amine NH2 Amine amine ethanamine
nitrile C ≡ N Nitrile nitrile propanenitrile
halogenoalkane F, Br, CI, I Halogeno chloroethane R - CI
Functionalgroup
H H H H
‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬
H - C – C – C – C – O-H
‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬
H H H H
Hydrocarbon skeleton Functional gp
IUPAC nomenclature
Systematic naming organic molecules
H CI O
‫׀‬ ‫׀‬ ‖
H - C – C – C - OH
‫׀‬ ‫׀‬
H H C1 – functional gp
C2 – substituent gp - CI
2 – chloropropanoic acid
Prefix Stem Suffix
Position and
substituent
Longest carbon
chain
Functional
gp
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3 2 1

2. H CH3 H H H
‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬
H - C - C – C – C – C – H
‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬
H H H H H
H H H H
‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬
H - C – C – C – C – O-H
‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬
H H H H
Hydrocarbon skeleton Functional gp
Hydrocarbon
Aliphatic Aromatic
Saturated Unsaturated
benzene alkylbenzene
H H
‫׀‬ ‫׀‬
H - C – C – H
‫׀‬ ‫׀‬
H H
H H
‫׀‬ ‫׀‬
C = C
‫׀‬ ‫׀‬
H H
Alkane Cycloalkane
Compound Ethane Ethanoic acid
Empirical formula CH3 CH2O
Molecular formula C2H6 C2H4O2
Full SF
Condensed SF CH3CH3 CH3COOH
Stereochemical
formula
(3D)
H H
‫׀‬ ‫׀‬
H - C – C – H
‫׀‬ ‫׀‬
H H
H O
‫׀‬ ‖
H - C - C - OH
‫׀‬
H
Organic Chemistry
Cycloalkene Alkene
IUPAC nomenclature
Ring form
Functionalgroup
Structural formula
2 – chloropropanoic acid
no aromatic ring
Systematic naming organic molecules
Prefix Stem Suffix
Position and
substituent
Longest carbon
chain
Functional
gp
H CI O
‫׀‬ ‫׀‬ ‖
H - C – C – C - OH
‫׀‬ ‫׀‬
H H C1 – functional gp
C2 – substituent gp - CI
CH3(CH2)3CH3
H H H H H
‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬
H - C - C – C – C – C – H
‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬
H H H H H
Use of parenthesis
Repeat CH2 x 3
CH3CH(CH3)(CH2)2CH3
Repeat CH2 x 2CH3 branch
H CH3 H CH3 H
‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬
H - C - C – C – C – C – H
‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬
H H H H H
CH3CH(CH3)CH2CH(CH3)CH3
CH3 branch
3 2 1
benzene ring
inside

3. IsomerismMolecules with same molecular formula but diff arrangement of atom
Two types of Isomerism
Positional Chain Isomer Functional Gp Isomer
C – C – C – C – OH
C4H10O1
StructuralIsomerism
• Same molecular formula
• Diff structural formula
• Diff arrangement of atom
Diff hydrocarbonchain skeleton
• Same molecular formula
• Same structuralformula
• Diff spatial arrangement ofatom
Stereoisomerism
Hydrocarbon Chain Isomer
Diff functional gp position Diff functional gp
C – C – C – OH
‫׀‬
CH3
C – C – C –C
‫׀‬
OH
C – C – C – C
‫׀‬
OH
C – C – C – C
‫׀‬
OH
C – C – C – O – C
Optical IsomerGeometric Isomer
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Compound Ethane Ethanoic acid
Empirical formula CH3 CH2O
Molecular formula C2H6 C2H4O2
Full SF
Condensed SF CH3CH3 CH3COOH
Stereochemical
formula
(3D)
Isomer Physical
property
Chemical
property
Structural isomer
- Hydrocarbon chain
- Functional gp position
- Functional gp
Different
Different
Different
Similar
Similar
Different
Geometrical isomer Different Similar
Optical isomer Similar Similar
H H
‫׀‬ ‫׀‬
H - C – C – H
‫׀‬ ‫׀‬
H H
H O
‫׀‬ ‖
H - C - C - OH
‫׀‬
H
Structural formula – arrangement atoms in molecule (2/3D)
H H
‫׀‬ ‫׀‬
H - C – C – H
‫׀‬ ‫׀‬
H H
CH3CH3
ethane
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4. Diff functional
gp position
C4H9OH
StructuralIsomerism
• Same molecular formula
• Diff structural formula
• Diff arrangement of atom
Diff hydrocarbon
chain skeleton
Diff functional
gp position
Diff functional gp
CH3-CH2-CH2-CH3
‫׀‬
OH
Butan–1-ol
CH3-CH-CH2-OH
‫׀‬
CH3
2-Methylpropan-1-ol
CH3
‫׀‬
CH3-C-OH
‫׀‬
CH3
CH3-CH2-CH-CH3
‫׀‬
OH
2-Methylpropan-2-ol Butan-2-ol
CH3-CH2-CH2-O-CH3
Methoxypropane
CH3-CH2-O-CH2-CH3
Ethoxyethane
7 structural isomers
CH3-CH-O-CH3
‫׀‬
CH3
CH3-CH2-CH2=CH2
C4H8
CH3-CH=CH-CH3
CH3-C=CH2
‫׀‬
CH3
CH2 – CH2
‫׀‬ ‫׀‬
CH2 - CH2
C4H9Br
CH3-CH2-CH2-CH2
‫׀‬
Br
CH3-CH2-CH-CH3
‫׀‬
Br
CH3
‫׀‬
CH3-C-Br
‫׀‬
CH3
CH3- CH-CH2
‫׀‬ ‫׀‬
CH3 Br
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C6H14
CH3-CH2-CH2-CH2-CH2-CH3 CH3-CH-CH2-CH2-CH3
‫׀‬
CH3
CH3-CH2-CH-CH2-CH3
‫׀‬
CH3
CH3
‫׀‬
CH3-C-CH2-CH3
‫׀‬
CH3
CH3- CH- CH-CH3
‫׀‬ ‫׀‬
CH3 CH3
Diff hydrocarbon
chain skeleton
Diff functional
gp position
Diff functional
gp
Diff hydrocarbon
chain skeleton
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4 structural isomers 4 structural isomers
5 structural isomers
Diff hydrocarbon
chain skeleton

5. StructuralIsomerism
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C3H6O
H
‫׀‬
CH3-CH2-C=O
O
‖
CH3-C-CH3
OH
‫׀‬
CH3-CH=C-H
OH
‫׀‬
CH2=CH-CH2
CH3-O-CH=CH2
C4H8O
CH3-CH2-CH2-C-H
‖
O
CH3 -CH2 -C-CH3
‖
O
CH3-CH - C-H
‫׀‬ ‖
CH3 O
CH2=CH-CH2-CH2-OH CH3-CH=CH-CH2-OH CH3-CH2-CH=CH-OHCH3-CH2-O-CH=CH2CH3-CH=CH-O-CH3
C5H10
CH2=CH-CH2-CH2-CH3
CH3-CH=CH-CH2-CH3CH2=C-CH2-CH3
‫׀‬
CH3
CH2=CH-CH-CH3
‫׀‬
CH3
CH3-CH=C-CH3
‫׀‬
CH3
CH2-CH-CH2-CH3
CH2
CH3-CH-CH-CH3
CH2
CH3
‫׀‬
CH2– C-CH3
CH2
CH2
CH2 CH2 ‫וּ‬
‫׀‬ ‫׀‬
CH2 –CH2
CH2 –CH-CH3
‫׀‬ ‫׀‬
CH2– CH2
Aldehyde Ketone Alkene/Alcohol Alkene/Alcohol Alkene/Ether
5 structural isomers
8 structural isomers
10 structural isomers
Cyclo – ring structure
• Same molecular formula
• Diff structural formula
• Diff arrangement of atom

6. C5H11Br
StructuralIsomerism
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CH3-CH2-CH2-CH2-CH2-Br CH3-CH2-CH2-CH-CH3
‫׀‬
Br
CH3-CH2-CH-CH2-CH3
‫׀‬
Br
CH3-CH-CH2-CH2-Br
‫׀‬
CH3
CH3-CH2-CH-CH2-Br
‫׀‬
CH3
CH3
‫׀‬
CH3–CH–CH-CH3
‫׀‬
Br
CH3
‫׀‬
CH3-CH2- C-CH3
‫׀‬
Br
CH3
‫׀‬
CH3-C-CH2-Br
‫׀‬
CH3
CH3- CH- CH-Br
‫׀‬ ‫׀‬
CH3 CH3
CH3 CH3
‫׀‬ ‫׀‬
CH3- C - CH2
‫׀‬
Br
CH3
‫׀‬
CH3-CH2- C-Br
‫׀‬
CH3
C3H6O2
CH3-CH2-C-OH
‖
O
CH3 - C- O-CH3
‖
O
H- C-O-CH2-CH3
‖
O
CH2- CH = CH
‫׀‬ ‫׀‬
OH OH
CH=C-CH3
Ι Ι
OH OH
HO-C=CH-CH3
‫׀‬
OH
HO-CH-CH=CH2
‫׀‬
OH
OH
‫׀‬
CH3-CH–C-H
‖
O
CH2- C = CH2
‫׀‬ ‫׀‬
OH OH
OH
‫׀‬
CH2-CH2-CH
‖
O
CH3-O-CH2-CH
‖
O
CH2 = C-O-CH3
‫׀‬
OH
CH2= CH-O-CH2
‫׀‬
OH
CH=CH-O-CH3
‫׀‬
OH
2-bromo-3-methylbutane 2-bromo-2-methylbutane
8 structural isomers
Alcohol / Alkene
Carboxylic acid Ester Aldehyde / Alcohol
Alcohol / Alkene / Ether
14 structural isomers
• Same molecular formula
• Diff structural formula
• Diff arrangement of atom

7. H H H H H
‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬
H - C – C – C - C – C – F
‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬
H CH3 H H H
H CH3
‫׀‬ ‫׀‬
CI – C – C – C
‫׀‬ ‫׀‬
H CH3
H CH3 H
‫׀‬ ‫׀‬ ‫׀‬
H - C – C – C – Br
‫׀‬ ‫׀‬ ‫׀‬
H CH3 H
H CH3 H H
‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬
H - C – C – C - C – H
‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬
I H H H
H C
‫׀‬ ‫׀‬
C – C – C – C - C
‫׀‬
CI
C CH3 H
‫׀‬ ‫׀‬ ‫׀‬
H - C – C – C – H
‫׀‬ ‫׀‬ ‫׀‬
CI H H
CH3
‫׀‬
CI – C – C – C
‫׀‬
H
H H CI
‫׀‬ ‫׀‬ ‫׀‬
H - C – C - C – H
‫׀‬ ‫׀‬ ‫׀‬
H CH3 H
Halogenoalkane and Nomenclature
H
‫׀‬
CH3 – C – CI
‫׀‬
H
Types of halogenoalkane
Primary 1 0
NO alkyl /1 alkyl/R gp bond to C attach to halogen
H CH3 H
‫׀‬ ‫׀‬ ‫׀‬
H - C – C – C – CI
‫׀‬ ‫׀‬ ‫׀‬
H CH3 H
H
‫׀‬
H - C – CI
‫׀‬
H
Secondary 2 0
2 alkyl/R gp bond to C attach to halogen
H
‫׀‬
CH3 – C – CI
‫׀‬
CH3
H H H
‫׀‬ ‫׀‬ ‫׀‬
H - C – C – C – H
‫׀‬ ‫׀‬ ‫׀‬
H CI H
H
‫׀‬
R – C – CI
‫׀‬
R
Tertiary 3 0
3 alkyl/R gp bond to C attach to halogen
CH3
‫׀‬
CH3 – C – CI
‫׀‬
CH3
H CH3 H
‫׀‬ ‫׀‬ ‫׀‬
H - C – C – C – H
‫׀‬ ‫׀‬ ‫׀‬
H CI H
R
‫׀‬
R – C – CI
‫׀‬
R
H H H
‫׀‬ ‫׀‬ ‫׀‬
H - C – C – C – H
‫׀‬ ‫׀‬ ‫׀‬
H CI H
H CH3 H
‫׀‬ ‫׀‬ ‫׀‬
H - C – C – C – C
‫׀‬ ‫׀‬ ‫׀‬
H CI H
CH3
‫׀‬
CH3 – C – CI
‫׀‬
CH3
H CH3 H
‫׀‬ ‫׀‬ ‫׀‬
H - C – C – C – H
‫׀‬ ‫׀‬ ‫׀‬
H Br H
C
‫׀‬
CI – C – C – C
‫׀‬
C – C
Br CH3
‫׀‬ ‫׀‬
C – C – C – C – C
‫׀‬ ‫׀‬
CH3 CH3
C CI C
‫׀‬ ‫׀‬ ‫׀‬
C – C – C – C – C
‫׀‬
C
Primary 1 o
Secondary2 o
Tertiary 3 o
H H H
‫׀‬ ‫׀‬ ‫׀‬
H - C – C - C – H
‫׀‬ ‫׀‬ ‫׀‬
H H F
H H CH3 H H
‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬
H – C – C - C – C – C - H
‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬
H CI CH3 H H
H
‫׀‬
CH3 – C – CI
‫׀‬
CH3

8. C
‫׀‬
HO – C – C – C
‫׀‬
C – C
H CH3
‫׀‬ ‫׀‬
HO – C – C – C
‫׀‬ ‫׀‬
H CH3
H H H H H
‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬
H - C – C – C - C – C – OH
‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬
H CH3 H H H
H CH3 H
‫׀‬ ‫׀‬ ‫׀‬
H - C – C – C – OH
‫׀‬ ‫׀‬ ‫׀‬
H CH3 H
H CH3 H H
‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬
H - C – C – C - C – H
‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬
OH H H H
H C
‫׀‬ ‫׀‬
C – C – C – C - C
‫׀‬
OH
C CH3
‫׀‬ ‫׀‬
H - C – C – C – H
‫׀‬ ‫׀‬ ‫׀‬
OH H H
CH3
‫׀‬
HO – C – C – C
‫׀‬
H
H H OH
‫׀‬ ‫׀‬ ‫׀‬
H - C – C - C – H
‫׀‬ ‫׀‬ ‫׀‬
H CH3 H
Alcohol and Nomenclature
H
‫׀‬
CH3 – C – OH
‫׀‬
H
Types of alcohol
Primary 1 0
NO alkyl /1 alkyl/R gp bond to C attach to OH
H CH3 H
‫׀‬ ‫׀‬ ‫׀‬
H - C – C – C – OH
‫׀‬ ‫׀‬ ‫׀‬
H CH3 H
H
‫׀‬
H - C – OH
‫׀‬
H
Secondary 2 0
2 alkyl/R gp bond to C attach to OH
H
‫׀‬
CH3 – C – OH
‫׀‬
CH3
H H H
‫׀‬ ‫׀‬ ‫׀‬
H - C – C – C – H
‫׀‬ ‫׀‬ ‫׀‬
H OH H
H
‫׀‬
R – C – OH
‫׀‬
R
Tertiary 3 0
3 alkyl/R gp bond to C attach to OH
CH3
‫׀‬
CH3 – C – OH
‫׀‬
CH3
H CH3 H
‫׀‬ ‫׀‬ ‫׀‬
H - C – C – C – H
‫׀‬ ‫׀‬ ‫׀‬
H OH H
R
‫׀‬
R – C – OH
‫׀‬
R
H H H
‫׀‬ ‫׀‬ ‫׀‬
H - C – C – C – H
‫׀‬ ‫׀‬ ‫׀‬
H OH H
H CH3 H
‫׀‬ ‫׀‬ ‫׀‬
H - C – C – C – C
‫׀‬ ‫׀‬ ‫׀‬
H OH H
CH3
‫׀‬
CH3 – C – OH
‫׀‬
CH3
H CH3 H
‫׀‬ ‫׀‬ ‫׀‬
H - C – C – C – H
‫׀‬ ‫׀‬ ‫׀‬
H OH H
OH CH3
‫׀‬ ‫׀‬
C – C – C – C – C
‫׀‬ ‫׀‬
CH3 CH3
C OH C
‫׀‬ ‫׀‬ ‫׀‬
C – C – C – C – C
‫׀‬
C
Primary 1 o
Secondary2 o
Tertiary 3 o
H H H
‫׀‬ ‫׀‬ ‫׀‬
H - C – C - C – H
‫׀‬ ‫׀‬ ‫׀‬
H H OH
H H CH3 H H
‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬
H – C – C - C – C – C - H
‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬
H OH CH3 H H
H
‫׀‬
CH3 – C – OH
‫׀‬
CH3

9. H H H H H
‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬
H - C – C – C - C – C –NH2
‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬
H CH3 H H H
H CH3
‫׀‬ ‫׀‬
NH2 – C – C – C
‫׀‬ ‫׀‬
H CH3
H CH3 H
‫׀‬ ‫׀‬ ‫׀‬
H - C – C – C – NH2
‫׀‬ ‫׀‬ ‫׀‬
H CH3 H
H CH3 H H
‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬
H - C – C – C - C – H
‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬
NH2 H H H
H C
‫׀‬ ‫׀‬
C – C – C – C - C
‫׀‬
NH2
C CH3 H
‫׀‬ ‫׀‬ ‫׀‬
H - C – C – C – H
‫׀‬ ‫׀‬ ‫׀‬
NH2 H H
C
‫׀‬
NH2 – C – C – C
‫׀‬
H
H H NH2
‫׀‬ ‫׀‬ ‫׀‬
H - C – C - C – H
‫׀‬ ‫׀‬ ‫׀‬
H CH3 H
Amines and Nomenclature
H
‫׀‬
CH3 – C – NH2
‫׀‬
H
Types of amines
Primary 1 0
NO alkyl /1 alkyl/R gp bond to C attach to nitrogen
H CH3 H
‫׀‬ ‫׀‬ ‫׀‬
H - C – C – C – NH2
‫׀‬ ‫׀‬ ‫׀‬
H CH3 H
H
‫׀‬
H - C – NH2
‫׀‬
H
Secondary 2 0
2 alkyl/R gp bond to C attach to nitrogen
H
‫׀‬
CH3 – C – NH2
‫׀‬
CH3
H H H
‫׀‬ ‫׀‬ ‫׀‬
H - C – C – C – H
‫׀‬ ‫׀‬ ‫׀‬
H NH2 H
H
‫׀‬
R – C – NH2
‫׀‬
R
Tertiary 3 0
3 alkyl/R gp bond to C attach to nitrogen
CH3
‫׀‬
CH3 – C – NH2
‫׀‬
CH3
H CH3 H
‫׀‬ ‫׀‬ ‫׀‬
H - C – C – C – H
‫׀‬ ‫׀‬ ‫׀‬
H NH2 H
R
‫׀‬
R – C – NH2
‫׀‬
R
H H H
‫׀‬ ‫׀‬ ‫׀‬
H - C – C – C – H
‫׀‬ ‫׀‬ ‫׀‬
H NH2 H
H CH3 H
‫׀‬ ‫׀‬ ‫׀‬
H - C – C – C – C
‫׀‬ ‫׀‬ ‫׀‬
H NH2 H
CH3
‫׀‬
CH3 – C – NH2
‫׀‬
CH3
H CH3 H
‫׀‬ ‫׀‬ ‫׀‬
H - C – C – C – H
‫׀‬ ‫׀‬ ‫׀‬
H NH2 H
C
‫׀‬
NH2 – C – C – C
‫׀‬
C – C
NH2 CH3
‫׀‬ ‫׀‬
C – C – C – C – C
‫׀‬ ‫׀‬
CH3 CH3
C NH2 C
‫׀‬ ‫׀‬ ‫׀‬
C – C – C – C – C
‫׀‬
C
Primary 1 o
Secondary2 o
Tertiary 3 o
H H H
‫׀‬ ‫׀‬ ‫׀‬
H - C – C - C – H
‫׀‬ ‫׀‬ ‫׀‬
H H NH2
H H CH3 H H
‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬
H – C – C - C – C – C - H
‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬
H NH2 CH3 H H
H
‫׀‬
CH3 – C – NH2
‫׀‬
CH3

10. Delocalizationof electrons
Resonance
• Describing delocalizationof electrons within a molecule/polyatomic ion
where bonding cannot be express by ONE single Lewis structure
• Delocalization of π bond – π electrons spread over more than 2 nuclei
• π electrons are shared/spread– more stable
Resonance structuresbenzene
Benzene
6HC6
resonance structure 1 resonance structure 2
Resonance hybrid
• All bonds C6H6 are identical in length/ strength
• Hybrid of 2 resonance structures
• No C-C (single) or C=C (double) bonds found
• Only C ----- C bond
• Intermediate character bet single/double bond
• Bond Order =
• Unhybridised p orbital
• Delocalization electrons above below plane
• sp2 hybridization on carbon center
1.5
Click here to view
Delocalized electrons
Kekulé structure
Cyclohexa- 1,3,5 triene
χ ✓
double/single bonds bet them
Benzene
Hexagonal,
planar
Resonance Hybrid more stable than any of the resonance structure ✓
Click here to view
Kekule
✓
or

11. Resonance/Delocalization Energy
ΔH cyclohexene = -120 kJmol-1
ΔH cyclohexa1,3,5 triene = - 360 kJmol-1
ΔH Benzene = - 208kJmol-1
Enthalpy change hydrogenation
χ
- Benzene lower in energy by 152 kJ
- More stable due to delocalization
of π electrons
- 152 kJ
- 152
C-C
Single bond
C = C
Double bond
C = C
Benzene
Bond length/pm 154 134 140
Bond
enthalpy/kJmol-1
346 614 507
Evidence for Benzene structure
1
2
Click here evidence against Kekule
• X ray hit benzene crystal
• Interact with electron (electron density map)
• X ray diffraction produced
• Bond length measured
X ray crystallography
NO single/double bond detected ✓
✓
3 No addition rxn in benzene C=C
Addition rxn
Substitution rxn
NO double bond
-240
……
-360
- 208
ΔH cyclohexa 1,3 diene = -240 kJmol-1
+
✓
✓
+ Br - Br →✓