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IB Chemistry on Structural Isomers and Benzene Structure

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  • 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

    Functional group

    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

    Organic software for 3D model Click here resources Rasmol

    Click here download Rasmol Click here download PyMol Click here download ACD Lab Click here download Jmol

    3 2 1

    http://www.heckgrammar.co.uk/index.php?p=10311http://www.heckgrammar.co.uk/index.php?p=10311http://www.rasmol.org/http://www.rasmol.org/http://www.pymol.org/http://www.pymol.org/animatehttp://www.acdlabs.com/http://www.acdlabs.com/http://jmol.sourceforge.net/http://jmol.sourceforge.net/

  • 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

    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 2 CH3 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

  • Isomerism Molecules 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 Isomer Geometric Isomer

    Click here khan organic videos.

    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

    Display full SF Condensed SF Ball/stick model Spacefilling

    Click here chemical search.

    https://www.youtube.com/watch?v=1LdFePZHAyYhttps://www.youtube.com/watch?v=1LdFePZHAyYhttp://www.chemspider.com/Chemical-Structure.109861.htmlhttp://www.chemspider.com/Chemical-Structure.109861.html

  • 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

    Butan1-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

    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

    http://chemwiki.ucdavis.edu/Organic_Chemistry/Organic_Chemistry_With_a_Biological_Emphasis/Chapter_03:_Conformations_and_Stereochemistry/Section_3.3:_Stereoisomerism_%E2%80%93_chirality,_stereocenters,_enantiomershttp://chemwiki.ucdavis.edu/Organic_Chemistry/Organic_Chemistry_With_a_Biological_Emphasis/Chapter_03:_Conformations_and_Stereochemistry/Section_3.3:_Stereoisomerism_%E2%80%93_chirality,_stereocenters,_enantiomershttp://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/intro1.htmhttp://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/intro1.htm

  • Structural Isomerism

    Click 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-OH CH3-CH2-O-CH=CH2 CH3-CH=CH-O-CH3

    C5H10

    CH2=CH-CH2-CH2-CH3 CH3-CH=CH-CH2-CH3 CH2=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

    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

    http://chemwiki.ucdavis.edu/Organic_Chemistry/Organic_Chemistry_With_a_Biological_Emphasis/Chapter_03:_Conformations_and_Stereochemistry/Section_3.3:_Stereoisomerism_%E2%80%93_chirality,_stereocenters,_enantiomershttp://chemwiki.ucdavis.edu/Organic_Chemistry/Organic_Chemistry_With_a_Biological_Emphasis/Chapter_03:_Conformations_and_Stereochemistry/Section_3.3:_Stereoisomerism_%E2%80%93_chirality,_stereocenters,_enantiomershttp://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/intro1.htmhttp://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/intro1.htm

  • C5H11Br

    Structural Isomerism

    Click 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

    CH3CHCH-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

    OH OH

    HO-C=CH-CH3

    OH

    HO-CH-CH=CH2

    OH

    OH

    CH3-CHC-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

    http://chemwiki.ucdavis.edu/Organic_Chemistry/Organic_Chemistry_With_a_Biological_Emphasis/Chapter_03:_Conformations_and_Stereochemistry/Section_3.3:_Stereoisomerism_%E2%80%93_chirality,_stereocenters,_enantiomershttp://chemwiki.ucdavis.edu/Organic_Chemistry/Organic_Chemistry_With_a_Biological_Emphasis/Chapter_03:_Conformations_and_Stereochemistry/Section_3.3:_Stereoisomerism_%E2%80%93_chirality,_stereocenters,_enantiomershttp://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/intro1.htmhttp://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/intro1.htm

  • 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 bond electrons spread over more than 2 nuclei 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

    Kekul structure

    Cyclohexa- 1,3,5 triene

    double/single bonds bet them

    Benzene

    Hexagonal, planar

    Resonance Hybrid more stable than any of the resonance structure

    Click here to view

    Kekule

    or

    https://www.youtube.com/watch?v=Gk49Y1bTPu4https://www.youtube.com/watch?v=Gk49Y1bTPu4https://www.youtube.com/watch?v=q_vK6kMoqOkhttps://www.youtube.com/watch?v=q_vK6kMoqOk

  • Resonance/Delocalization Energy

    H cyclohexene = -120 kJmol-1

    H cyclohexa1,3,5 triene = - 360 kJmol-1

    H Benzene = - 208kJmol-1

    Enthalpy change hydrogenation

    - Benzene lower in energy by 152 kJ - More stable due to delocalization of 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

    H cyclohexa 1,3 diene = -240 kJmol-1

    +

    + Br - Br

    http://www.epmagazine.org/storage/165/benzene-evidence.aspx

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