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Prepared by Lawrence Kok
Tutorial on Structural isomers and Benzene Structures
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 CnH2nOorR-CO-R
aldehyde C = O ׀ H
Aldehyde anal ethanal CnH2nOorR -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
Functional group
H H H H ׀ ׀ ׀ ׀ H - C – C – C – C – O-H׀ ׀ ׀ ׀ H H H H
Hydrocarbon skeleton Functional gp
IUPAC nomenclatureSystematic 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
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 AlkeneIUPAC nomenclature
Ring form
Functional group
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
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
Structural Isomerism
• Same molecular formula• Diff structural formula• Diff arrangement of atom
Diff hydrocarbon chain skeleton
• Same molecular formula• Same structural formula• Diff spatial arrangement of atom
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
DifferentDifferentDifferent
SimilarSimilar
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
Display full SF Condensed SF Ball/stick model Spacefilling
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Diff functional gp position
C4H9OH
Structural Isomerism
• 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-CH3CH3-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
Click here for organic notes
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
Click here virtual organic text
4 structural isomers 4 structural isomers
5 structural isomers
Diff hydrocarbon
chain skeleton
Structural Isomerism
• Same molecular formula• Diff structural formula• Diff arrangement of atomClick here for organic notes Click here virtual organic text
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=CH2 CH3-CH=CH-O-CH3
C5H10
CH2=CH-CH2-CH2-CH3CH3-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 ּו ׀ ׀
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
C5H11Br
Structural Isomerism
• Same molecular formula• Diff structural formula• Diff arrangement of atomClick here for organic notes Click here virtual organic text
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 ΙOH 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
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
Secondary 2 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
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
Secondary 2 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
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
Secondary 2 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
Delocalization of electrons
Resonance • Describing delocalization of 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 structures benzene
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
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-CSingle bond
C = CDouble bond
C = CBenzene
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 →✓
Acknowledgements
Thanks to source of pictures and video used in this presentation
Thanks to Creative Commons for excellent contribution on licenseshttp://creativecommons.org/licenses/
Prepared by Lawrence Kok
Check out more video tutorials from my site and hope you enjoy this tutorialhttp://lawrencekok.blogspot.com