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    2012 Gregory R Cook

    Chapter 04Alcohols and Alkyl Halides

    part 01

    CHEM 341: Spring 2012

    Prof. Greg Cook

    cook.chem.ndsu.nodak.edu/chem341

    Wednesday, February 8, 12

    http://cook.chem.ndsu.nodak.edu/chem341http://cook.chem.ndsu.nodak.edu/chem341

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    Functional Groups

    A functional group is a structural feature in a molecule that has characteristic reactivity.

    A functional group has similar behavior in every molecule that contains it.

    2

    Carbon-Carbon Multiple Bonds

    Alkenes - double bonds

    CH2 CH2

    Alkynes - triple bonds

    C C

    Arenes - aromatic rings

    Carbon-Other atom Single Bonds

    OH

    Alcohols

    Br

    Hallides

    NH2

    Amines

    OCH3

    Ethers

    SH

    Thiols

    SCH3

    Sulfides

    Carbon-Oxygen Double Bonds (Carbonyls)

    H

    AldehydeO

    KetoneO

    OH

    AcidO

    OCH3

    EsterO

    NH2

    AmideO

    Cl

    Acid HalideO

    H H

    Wednesday, February 8, 12

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    2012 Gregory R Cook

    Functional Groups

    A functional group is a structural feature in a molecule that has characteristic reactivity.

    A functional group has similar behavior in every molecule that contains it.

    2

    Carbon-Carbon Multiple Bonds

    Alkenes - double bonds

    CH2 CH2

    Alkynes - triple bonds

    C C

    Arenes - aromatic rings

    Carbon-Other atom Single Bonds

    OH

    Alcohols

    Br

    Hallides

    NH2

    Amines

    OCH3

    Ethers

    SH

    Thiols

    SCH3

    Sulfides

    Carbon-Oxygen Double Bonds (Carbonyls)

    H

    AldehydeO

    KetoneO

    OH

    AcidO

    OCH3

    EsterO

    NH2

    AmideO

    Cl

    Acid HalideO

    H HR OH R Xalcohols alkyl halides

    Wednesday, February 8, 12

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    2012 Gregory R Cook

    Reactions of Functional Groups

    3

    H XR OH + H OHR X +

    OHR X + R OH + X

    X XR H + H XR X +

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    2012 Gregory R Cook

    General Reaction Classes

    Addition Reactions - two or more molecules combine to form a new product

    Elimination Reactions - a molecule breaks apart into two or more molecules

    Substitution Reactions - part of a molecule is substituted for another group

    Rearrangement Reactions - A molecule does not gain or lose atoms, but reorganizes its bonds or groups. Also called isomerization.

    4

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    General Reaction Classes

    Addition Reactions

    Elimination Reactions

    Substitution Reactions

    Rearrangement Reactions

    5

    A + B C C CH

    H

    H

    H+ H2 cat. C C

    H

    HHH

    H

    H

    CA B + BA C + H3C Cl + OH H3C OH + Cl

    BA heatO O

    A + BC cat.OH

    H

    + HOH

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    2012 Gregory R Cook

    Organic halogen compounds are found in many places from common solvents for chemistry and industry, to refrigerants (largely banned for their ozone destruction properties) and natural products.

    Alkyl Halides

    6

    CH2Cl2CHCl3CH2Cl-CH2Cl

    commonsolvents

    CFCs(chlorofluorocarbons)

    CF2Cl2

    natural products(epibatidine)

    NH

    N

    Cl

    Wednesday, February 8, 12

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    Alkyl halides are often named using common naming (functional class) considering the alkyl group as a substituent on the halide.

    Alkyl Halide Nomenclature

    7

    methyl bromide

    H3C BrI

    cyclopentyl iodide 1-methylpropyl chloride

    Cl

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    IUPAC naming is best using the carbon chain as the parent and the halogen as a halo- substituent

    Alkyl Halide Nomenclature

    8

    bromomethane

    H3C BrI

    iodocyclopentane 2-chlorobutane

    Cl

    Br Br

    4-bromo-2-methylhexane 2-bromo-4-methylhexane

    Wednesday, February 8, 12

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    Alcohols are often named using common naming (functional class) considering the alkyl group as a substituent on the OH functional group.

    Alcohols

    9

    methyl alcohol

    H3C OHOH

    cyclopentyl alcohol isopropyl alcohol

    OH

    Wednesday, February 8, 12

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    IUPAC naming is best using the carbon chain as the parent and replacing the -ane ending with -anol

    note: alcohols outrank alkyl substituents

    Alcohol Nomenclature

    10

    methanol

    H3C OHOH

    cyclopentanol 2-propanol

    OH

    OH OH

    5-methyl-3-hexanol 4-methyl-2-hexanol

    Wednesday, February 8, 12

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    Alcohols and alkyl halides are classified according to the degree of alkyl substituion on the carbon the functional group is attached

    Classes of Alkyl Halides and Alcohols

    11

    OH

    1-propanola primary alcohol

    2-chloro-2-methylbutanea tertiary halide (chloride)

    Cl OH

    trans-3-methylcyclopentanola secondary alcohol

    Wednesday, February 8, 12

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    Reactivity is dominated by the polarity of the C-X bond

    Properties of Alkyl Halides

    12

    fluoromethane CH3-F 1.85 1.39 108

    chloromethane CH3-Cl 1.87 1.78 84

    bromomethane CH3-Br 1.81 1.93 70

    iodomethane CH3-I 1.62 2.14 56

    diopole moment(Debyes)

    bond length()

    bond strength(kcal/mol)

    = 1.9 D

    C Cl

    H

    H

    H

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    Acohols are polar but have other reactive features

    Properties of Alcohol

    13

    weakly acidic

    RO

    H

    weakly basic

    = 1.7 D

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    Boiling Points of Halides and Alcohol

    14

    Wednesday, February 8, 12

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    Intermolecular Forces

    15

    Induced dipole/induced dipole (London forces, van der Waals attraction)

    Dipole/induced dipole forces Diplole/Dipole forces

    Wednesday, February 8, 12

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    Intermolecular Forces

    16

    bp -24 C

    RO

    H

    = 1.7 D = 1.9 D

    C Cl

    H

    H

    H

    bp 65 C

    Wednesday, February 8, 12

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    At about 5 kcal/mol, H-bonds are weaker than covalent bonds but stronger than many other intermolecular forces

    Hydrogen Bonding

    17

    RO

    H

    +

    R

    O H +

    hydrogenbond

    R

    OH+

    hydrogenbond

    Wednesday, February 8, 12

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    Polarizability - the ability to distort (polarize) electrons in a bond

    Polarizability

    18

    chloromethanebp -24 C

    C Cl

    HH

    H

    C Cl

    ClH

    H

    C Cl

    ClCl

    H

    C Cl

    ClCl

    Cl

    dichloromethanebp 40 C

    trichloromethanebp 61 C

    tetrachloromethanebp 77 C

    fluroethanebp -32 C

    C F

    HH

    C

    1,1-difluoroethanebp -25 C

    1,1,1-trifluoroethanebp -47 C

    hexafluoroethanebp -77 C

    HH

    H

    C F

    FH

    CH

    H

    H

    C F

    FF

    CH

    H

    H

    C F

    FF

    CF

    F

    F

    Wednesday, February 8, 12

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    Alcohols are similar to water but the solubility decreases as the hydrocarbon chain increases

    Alcohol Solubility

    19

    CH3 OH

    AlcoholSolubility in Water(g/100 g H2O)

    CH3CH2 OH

    OH

    OH

    OH

    OH

    OH

    OH

    OH

    miscible

    miscible

    miscible

    9

    2.7

    0.6

    0.18

    0.054

    insoluble

    Carbons

    1

    2

    3

    4

    5

    6

    7

    8

    10

    Wednesda

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