Organic Chemistry - PowerPoint 4

Document Sample
Organic Chemistry - PowerPoint 4 Powered By Docstoc
					   Organic Chemistry
Study of carbon and its compounds (excluding
  such compounds as CO2, carbonates, and
            hydrogen carbonates)

Labs                                 Chemical Equations
#29 Aspirin Synthesis and Analysis   Chapter 6
           Carbon is central atom in organic
           Has three allotropes (different forms)
             Graphite (layers of sp2 bonded carbon atoms in
             6-membered rings which form flat sheets, each
             layer weakly bonded              to another with
             pi bonding)
             Diamonds (tetrahedrally bonded carbon atoms in
             covalent crystal of extraordinary hardness)
             Buckministerfullerene (spheres of 60 carbon
             atoms covalently bonded together)

8/9/2012                                                        2
           Four valence electrons/forms four bonds
           (combination of single, double, triple bonds)
             Never nonbonding pair
             Can form four single bonds
               Tetrahedral, sp3
             Can form three bonds
               Trigonal planar, sp2
               Structure involves one double bond and two single bonds
             Can form two bonds
               Linear, sp
               Structure with either two double bonds (CO2) or one single
               and one triple bond (HCN)

8/9/2012                                                                    3
      Comparison of organic and inorganic
              I-generally soluble in polar solvents (water)
              O-generally soluble in nonpolar solvents (benzene)
              I-many conduct electric current when dissolved in solution because of
              ionization/dissociation of solute
              O-generally nonelectrolytes
           Melting and boiling points
              I-generally higher because of stronger intermolecular forces
              I-generally react more rapidly because they require fewer bond
              rearrangements than organic compounds
           Rate of reaction
              I-fast, no catalyst needed
              O-slow, catalyst needed

8/9/2012                                                                              4
                        Formula writing
   Molecular formula
           How many atoms of each
           element are present
           No info about how atoms
           are connected
   Dashed structural formula
           Straight lines represent
           chemical bonds
           Displays connections
           among atoms
   Condensed structural
           Atoms written without
           Hydrogen atoms written to
           right of atom to which they
           are connected

8/9/2012                                  5
           Only C/H
           Form basis of all other organic compounds
           Obtained from refining of petroleum by fractional
           Hydrocarbons w/related structures/properties
           usually separated into homologous series
             Each member of series differs from next member by
             single carbon atom
             ***With each successive member, melting and
             boiling points usually increase steadily

8/9/2012                                                         6
           Hydrocarbons are divided into two
            Aromatic-contain one or more benzene rings
            Aliphatic-do not contain benzene rings

8/9/2012                                                 7

Saturated hydrocarbons
    All single bonds
                     Alkanes (paraffins)
           Only single bonds between carbon atoms
           General formula: CnH2n+2
           As #C atoms increases
             London forces between molecules become stronger
             More energy needed to break intermolecular forces
             Progression from
                Gas (less than 5 Cs)
                to liquid (5-15 Cs)-gasoline, kerosene, nonpolar
                solvents, cleaning agents
                to solid (16 or more Cs)-paraffins, wax in candles

8/9/2012                                                             9
           Methane    CH4      gas
           Ethane     C2H6     gas
           Propane    C3H8     gas
           Butane     C4H10    gas
           Pentane    C5H12    liquid
           Hexane     C6H14    liquid
           Heptane    C7H16    liquid
           Octane     C8H18    liquid
           Nonane     C9H20    liquid
           Decane     C10H22   liquid
           Eicosane   C20H42   solid
8/9/2012                                10
           Simplest member-methane (CH4)-tetrahedral molecule
           with four sp3 hybridization of carbon atom
           Ending '-ane' is common to all alkanes
           Rather unreactive group-major use is a fuel in
           combustion reactions
           ***Melting and boiling points
             For straight-chain alkanes (normal)-M/BP increase
             regularly with number of carbon atoms in formula
             Branched structural isomers-lower M/BP than normal
             alkanes w/same number of carbon atoms
             Increased branching-decreases M/BP

8/9/2012                                                          11
           IUPAC-International Union of Pure and
           Applied Chemistry
             Organic compounds considered derivatives of
             parent hydrocarbons
             Full name determined by modifying name of
             parent structure according to functional groups
             attached to parent
             Select longest continuous carbon chain
               Count carbons in chain to determine parent name

8/9/2012                                                         12
           Substituents (groups attached to main chain)
           given lowest #s possible (# C from either end)
            Alkyl groups
              Formed when H atom is removed from alkane
              Make straight-chain hydrocarbon into branched-
              chain hydrocarbon
              Named by attaching –yl to prefix that indicates
              how many C atoms group has
                 CH3 (methyl)
                 CH3CH2- or C2H5 (ethyl)
                 CH3CH2CH2- or C3H7 (propyl)
            Halogenated HCs (fluoro/chloro/bromo/iodo)
            NH2– (amino), NO2– (nitro), and CH2CH– (vinyl)

8/9/2012                                                        13
           Substituents assigned #C to which they are
           Name of compound-name of parent chain
           preceded by name and # of substituents, arranged
           in alphabetical order
           If substituent occurs more than once in molecule,
           prefixes, di-, tri-, tetra, etc., used to indicate how
           many times it occurs
           If substituent occurs 2x on same C, # of substituent

8/9/2012                                                            14
           Try these:

8/9/2012                15
                   Reactions of Alkanes
           Relatively unreactive
              At room temperature, do not react with acids, bases, or
              strong oxidizing agents
              Due to strength/lack of polarity of C-C/C-H bonds
              In presence of excess oxygen, alkane combusts
              completely to form CO2 and H2O as only products
              In presence of limited oxygen, CO or particles of soot
              may form
           CnH2n+2(g) + (1.5n+0.5)O2(g)  nCO2(g) + (n+1)H2(g)
                   CH4(g) + 2 O2(g)  CO2(g) + 2 H2(g)

8/9/2012                                                                16
           One type of atom/group replaced w/another
           Use halogens to form haloaklanes
             Halogen molecules split into single atoms (free
             radicals-electrons freed when double bond is
             broken) that replace Hs

             CH4(g) + Br2(g)  CH3Br(g) + HBr(g)

8/9/2012                                                       17

Alkane that has atoms bonded
    into ring configurations
           Same general formula as alkenes, CnH2n, but
           no double bonds

           Six carbon rings are most common but five-
           membered rings are also common, particularly
           in biochemical molecules

8/9/2012                                                  19
   Read 22.1, pp. 1043-1052
   Q pp. 1091-1093, #26, 27, 29, 30, 40, 44, 48

8/9/2012                                          20
Unsaturated hydrocarbons
 Contain double bond(s)
                    Alkenes (olefins)
           Contain C=C double bonds
             Saturated-organic compounds containing only
             single bonds between carbon atoms
             Unsaturated-organic compounds containing
             double or triple bonds between carbon atoms
           General formula: CnH2n
           Named with same root word as alkanes but
           all names end in "ene"
             Smallest-C2H4-ethene (ethylene)

8/9/2012                                                   22
           Select longest continuous chain of Cs w/double
             Parent structure assigned name of corresponding alkane
             with “-ene” instead of “-ane”
           # chain so position of double bond designated by
           lowest possible # assigned to first doubly bonded
           Some common names
             H2C=CH-R           vinyl
             H2C=CH-CH2-R       allyl
             H3C-CH=CH-R        propenyl

8/9/2012                                                              23
           Dienes-has two double bonds
             General formula: CnH2n-2
             Named in same manner as alkenes except –ene is
             replaced with –diene and two numbers must be used to
             indicate position of double bonds
             C=C=C                 cumulated double bonds (allenes)
             C=C-C=C               conjugated (alternating) double
             C=C-(CH2)n-C=C isolated (non-conjugated)
                                   double bonds

8/9/2012                                                              24
                   Markovnikov’s Rule
           Predicts which of two products formed when
           hydrohalogenation occurs
             Different products may be formed when double bonded
             Cs react w/unsymmetrical reagents (HCl, HBr, H-OH)
               H atom partially positive charge/halogens more EN atoms
               Positive group adds to carbon that has most hydrogen

8/9/2012                                                                 25

Unsaturated hydrocarbons
  Contain triple bond(s)
           Contain CC triple   Nomenclature
           bonds (one sigma          Named in same manner
           and two pi bonds)         as alkenes
           General formula           When both double/
           CnH2n–2                   triple bond present
           Name end w/"yne"
                                         Double bond given
                                         preference over
                                         triple bond when

8/9/2012                                                     27
           Reactions of Alkenes/Alkynes
           Addition reactions
             Alkynes are very reactive
             Double/triple bond more reactive than single
             Saturated compounds can be produced from
             unsaturated compounds
             Take place more rapidly than substitution
             reactions because pi bonds in alkenes/ alkynes
             more reactive than sigma bonds

8/9/2012                                                      28
           Addition of halogen atoms
           Common and relatively rapid

           Addition of hydrogen atoms
           Used to solidify liquid vegetable oils
           Slow/metal catalysts must be used

8/9/2012                                            29
   Read 22.2, pp. 1052-1055
   Q pg. 32, 34

8/9/2012                      30
Organic compounds with the same
  formulas but different structures
          and properties
                             Structural Isomers
            Molecules w/same molecular formula, but
            different structure
            Each has different physical and chemical

   arrangement of Carbon skeleton                 position of Functional group

                                    different Functional groups

8/9/2012                                                                         32
           Compound w/straight chain of carbon atoms (normal)
             letter n precedes name
             Butane (C4H10) can be straight chained, and branched

       Highest BP
       because largest
                                               (tetramethymethane or neopentane)
       London forces
                                                Lowest BP because it
                                                can interact at only few
                                                points (smaller London

8/9/2012                                                                           33
           Same formulas, same chemical bonds, but
           have different arrangements in space and
           molecules are not superimposable
             Geometric isomers
               Involves double bond, usually C=C, that does not allow
               free rotation about double bond
             Optical isomers
               Involves atom, usually carbon, bonded to four different
               atoms or groups of atoms
               Exist in pairs, where one isomer is mirror image of

8/9/2012                                                                 34
           Geometric Isomers (cis-/trans-)
                       of Alkenes
           Configuration: relative positions of atoms in
           C-C bond allows carbon atoms to rotate
           C=C bond is rigid structure
             Rotation would require constant breaking/
             reforming of pi bond
             Atoms bound to C=C can’t rotate (fixed
             orientation) to become other structure

8/9/2012                                                   35
    cis- configuration                   trans-configuration
           Like groups on same side of     Like groups on opposite
           double bond                     sides of double bond

8/9/2012                                                             36
           2 molecules have          Shape
           different physical          trans isomer
           properties/can be
           separated from one          essentially straight
           another                     molecules
           Straight-chain                 Deposit easily in
                                          artery walls
           molecules have
           higher MPs than             cis isomer has
           branched-chain              120o bend
           molecules                      More difficult to
             Arrange into orderly         deposit due to
             crystalline structure        bend

8/9/2012                                                      37
             Stereoisomer (enantiomers)
                   optical isomers
      4 different groups attached to central carbon atom
      Rotate polarized light in different directions
         Chirality: having handedness
         Form nonsuperimposable mirror images
         Dextrorotatory-to right-designated by D
         Levorotatory-to left-designated by L
         Identical physical properties (BP, MP, solubility)
         Almost identical chemical reactivity
         Often have different chemical reactivities in biological
         systems where overall shape of molecule is important

8/9/2012                                                            38
           Organic synthesis methods
           may be stereospecific
           resulting in exclusion
           production of one
           stereoisomer or the other
           Racemic mixtures result in a
           50:50 mixture of D/L isomers
              Do not rotate polarized light
              (chirality still present)
              Rotation due to D isomers is
              canceled by equal/opposite
              rotation of L isomers

8/9/2012                                      39
           Any stereoisomer that is not an enantiomer
             Pairs of isomers w/opposite configurations at one or more
             of the chiral centers, but not mirro images of each other
           Can have different physical properties and
           different reactivity

8/9/2012                                                                 40
           In alkane series-as #C atoms increases, # of
           possible structural isomers increases
             CH4, C2H6, C3H8      1 isomer
             C4H10                2
             C5H12                3
             C6H14                5
             C7H16                9
             C8H18                18
             C9H20                35
             C10H22               75
             C12H26               355
             C20H42               366,319

8/9/2012                                                  41
8/9/2012   42

Contains benzene ring
           Represented as 2 resonance structures:
             Unusually stable because double bonds
             are conjugated
             Electrons in pi orbitals delocalized,
             stabilizing structure
             Stability makes it difficult to break
             carbon-carbon bonds of benzene
               Typical reactions involve replacing H atoms
               (which aren’t usually written) with other
               functional groups

8/9/2012                                                     44
           Functional aryl group for
           benzene is –C6H5 (phenyl)
           Naming of monosubstituted
           benzenes is
           containing both
           aromatic/aliphatic units

8/9/2012                               45
           If more than one substituent present, indicate
           position of two groups relative to each other
           ortho- substituents on adjacent carbons
           meta- C between carbons w/substituents
           para- 2 Cs on ring between carbons with substituents
           (substituents are attached to carbons directly across

8/9/2012                                                           46
           Reactions of Aromatic Compounds
           Halogens react w/benzene by substitution
           reaction rather than addition reaction
             Atom/group of atoms replaces H in benzene ring

8/9/2012                                                      47
   Read 22.3, pp. 1055-1057
   Q pg. 1092-1093, #38, 50

8/9/2012                      48
       Molecules that have
substitutents (functional groups)
 that contain some atoms which
  are not carbon or hydrogen

    Hydrocarbon derivatives
Functional Groups

Double/triple bonds reactive

Contain alkane group/hydroxyl group, -OH
  Add –ol to name of parent hydrocarbon
                 Can be classified by:
           Position of –OH              • # –OH groups in
             Primary                      molecule (can’t be on
                Name prefixed “n-“ or     same C)
                “1-“                      • Glycerol
                Name prefixed “sec-“
                or “2-“
                                          • Glycol (diole)
                Name prefixed “tert-“
                or “3-“

8/9/2012                                                          53
                Reactions with alcohols
           Chemical reactions
           occur at OH, not at
           less reactive alkane
              C-O-H bonds are
              rather strong so –
              OH group does not
           Contain polar
           hydroxyl group, Od––
           Hd+, which
           participates in H
           bonding to
           neighboring alcohol
8/9/2012                                  54

Oxygen atom is singly bonded to
        two carbon atoms
           R = alkyl group
             Less reactive than other oxygen-containing
             compounds (oxygen bonded to 2 different
             carbon atoms, which diffuses polarity)
                Don’t undergo any important reactions
             Much less polar than ketones/aldehydes of
             similar size
                Lower boiling points/higher vapor pressures
                (more flammable than other organic
                compounds) than those of aldehydes/ketones

8/9/2012                                                      56
           Ethers and alcohols are structural
           Both dimethyl
           ether (general
           anesthetic) and
           ethanol have same
           chemical formula
           Boiling points
           shows that ethers
           are much more
           volatile than

8/9/2012                                        57
8/9/2012   58
           Prepared by dehydrating primary alcohol in
           presence of H2SO4 in condensation reaction

8/9/2012                                                59
Functional group is carbonyl
         group, -C=O
             found at end of alkane chain
           C of carbonyl group   Add –al to name of
           bonded to at least    parent HC
           one H atom              Methanal
           Produced from           (formaldehyde)-
           oxidation of 1o
                                   cinnamon flavor
                                   Vanillin-vanilla flavor

8/9/2012                                                     61
           Carbonyl group strong dipole
             But only smaller aldehydes soluble in water
               About as soluble in water as alcohols of comparable
               weight (due to oxygen, it can have H-bond)
             BP higher than similar molecular weight
             alkanes/ethers but lower than alcohols which are
             held together by H bonds
           Many have pleasant odors
           Easily oxidized to carboxylic acids

8/9/2012                                                             62
                   not terminal group
           Double-bonded oxygen is located on a
           nonterminal carbon atom
             No hydrogen atoms directly attached to
             carbonyl group
           Produced from oxidation of 2o alcohol

8/9/2012                                              63
      Generally less reactive than          aldehydes
           Requires breaking C-C bonds
           Takes place only under vigorous conditions
           Add –one to name of parent HC
             2-propanone (acetone)-nail polish remover,
             2,3-butanedione-butter flavoring
             Irone-odor of violets
             Muscone-musk oil-in perfumes

8/9/2012                                                  64

Carboxyl group is functional group and always
      located on terminal carbon of molecule
                     Carboxylic Acids
           Weakly acidic (H+ dissociates because EN of 2
           oxygen atoms on same C weakens O-H bond)
           CH3COOH(aq)  CH3COO–(aq) + H+(aq)
           Highly polar, exhibit H bonding
             Higher BP than alcohols of comparable molecular weight
           Lighter acids readily dissolve in water (H bond w/
           water molecules)
           Easily produced from aldehyde

8/9/2012                                                              66
           Add –oic and acid to name of parent HC
             Homologous series of organic acids can be
             generated starting with formic acid
                HCOOH-methanoic acid (formic acid)
                CH3COOH or HC2H3O2-ethanoic acid (acetic
                acid) 5-6% aqueous solution of ethanoic acid-
                CH3CH2COOH-propanoic acid
                CH3CH2CH2COOH-butanoic acid
             Fatty acids are carboxylic acids that contain
             more than four carbon atoms

8/9/2012                                                        67

        Functional group is COOR
R is alkyl group that replaces H atom of
             carboxylic acid group
           Molecules polar but     Source of
           can’t H bond with       odor/flavors in fruits
           one another             Very large esters
             Lower BP than         (polyesters) for
             carboxylic acids of   clothing
             similar weights
                                   Fats and oils
                                   (lipids) are esters
                                   of long-chained
                                   carboxylic acids
                                   (fatty acids) and

8/9/2012                                                    69
8/9/2012   70
            Hydrolysis of ester in presence of base
              Base reacts directly w/ester to split it
              into salt of organic acid and alcohol
       C2H5COOCH3 + NaOH  C2H5COONa + CH3OH

8/9/2012                                                 71

Organic bases w/—NH2 functional group-amino group
 May be considered as derivatives of ammonia (NH3)
           General formula R3N (R = H, alkyl group, or
           aromatic group)
             RNH2: primary amine
             R2NH: secondary amine
                 Both have H atoms attached to N, making them
                 capable of intermolecular H bonding
             R3N: tertiary amine (no H bonded to N, so no
             intermolecular H bonds form)

8/9/2012                                                        73
      IUPAC naming                     Are weak bases (like
           Longest chain to which      ammonia)
           amino group attached is     Most have unpleasant
           parent chain
           -e ending from parent
           chain dropped and –         Many drugs that affect
           amine added                 nervous system are
           If amino group on other     amines (nicotine,
           than terminal carbon, its   amphetamine, mescaline,
           position numbered           adrenaline, caffeine,

8/9/2012                                                         74
      Amino Acids

Carboxylic acid that contains one
    or more amino groups
                        Amino Acids
           Contain two functional groups
             –NH2 (basic end)
             –COOH (acidic end)
           Reaction between amino acids forms peptide

8/9/2012                                                76

Derivative of organic acid, in which amino
        group (-NH2) replaces –OH on
                carboxyl group
           Simple amides are solids at room temp
           High BP due to strong intermolecular H
           Named by dropping –oic acid from acid and
           adding –amide in its place

8/9/2012                                               78
   Read 22.4, pp. 1057-top 1064
   Q pp. 1093-1094, #51, 52, 55-60

8/9/2012                             79
Condensation Reactions
            Addition polymerization
      Polymers made of many small, repeating
      molecular units (monomers) in reaction called
      No other product formed
      Initiated by free radical (has unplaired electron)
      attacking and breaking double or triple (Π)
      bond of molecule to form new free radical
      Repetition thousands of times until two radicals
      react to form bond/no other radical

8/9/2012                                                   81
8/9/2012   82
               Condensation reactions
           Each reactant must have two functional
           groups, one acid and one base
             Either –OH or –NH2
             Or one monomer contains two acid groups and
             another contains two basic groups

8/9/2012                                                   83
8/9/2012   84
   Read 22.5-22.6, pp. 1064-1088
   Q pp. 1091-1095, #6 a/b, 61, 62, 65
   Do 1 additional exercise and 1 challenge problem
   Submit quizzes by email to me:
8/9/2012                                                                                      85

Shared By: