Chapter 26 Functional Groups and Organic Reactions

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Chapter 26Functional Groups and Organic Reactions

• Charles Page High School
• Dr. Stephen L. Cotton

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Section 26.1 - Introduction to Functional Groups

• OBJECTIVES
• Define a functional group, and give several
  examples.

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Section 26.1 - Introduction to Functional Groups

• OBJECTIVES
• Describe halocarbons, and the substitution
  reactions they undergo.

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Functional Groups

• Most organic chemistry involves substituents
• often contain O, N, S, or P
• also called functional groups- they are the
  chemically functional part of the molecule, and
  are the non-hydrocarbon part

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Functional Groups

• Functional group - a specific arrangement of
  atoms in an organic compound, that is capable of
  characteristic chemical reactions.
  
• What is the best way to classify organic
  compounds? By their functional groups.

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Functional Groups

• The symbol R is used to represent any carbon
  chains or rings
  
• Important Table 26.1, page 774 -- shows some of
  the major categories, and their functional
  groups
  
• Table 26.2, p. 775 - alkyl groups

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Halogen Substituents

• Halocarbons - class of organic compounds
  containing covalently bonded fluorine, chlorine,
  bromine, or iodine.
  
• Naming? Name parent as normal, add the halogen
  as a substituent (or prefix) - Examples on page
  774

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Halogen Substituents

• The more highly halogenated the compound is, the
  higher the b.p. (see Table 26.3, page 775)
  
• Few halocarbons found in nature
• but, readily prepared and used
• halothane (Fig. 26.3, p.776) and also the
  hydrofluorocarbons

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Substitution Reactions

• Organic reactions often much slower than
  inorganic reactions
  
• must break strong covalent bond
• trying to find new catalysts to use
• Substitution - an atom (or group of atoms)
  replaces another atom or group of atoms

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Substitution Reactions

• A halogen (shown as X) can replace a hydrogen
  to make a halocarbon
  
• R-H X2 ? R-X HX
• Sunlight is often a sufficient catalyst
• CH4 Cl2 ? CH3Cl HCl

UV light
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Substitution Reactions

• Treating benzene with a halogen? Page 776
• Halogens on carbon chains are readily displaced
  by hydroxide ions (OH1-) to make an alcohol a
  salt
  
• R-X OH1- ? R-OH X1-

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Substitution Reactions

• CH3-I KOH ? CH3-OH KI
• CH3CH2Br NaOH ? CH3CH2OH NaBr

Iodomethane
Methanol
Bromoethane
Ethanol
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Section 26.2Alcohols and Ethers

• OBJECTIVES
• Describe the structures and naming of alcohols
  and ethers

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Section 26.2Alcohols and Ethers

• OBJECTIVES
• Define an addition reaction, and give several
  examples.

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Section 26.2Alcohols and Ethers

• OBJECTIVES
• Compare the properties of alcohols and ethers.

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Alcohols

• Alcohols - a class of organic compounds with an
  -OH group
  
• The -OH functional group in alcohols is called a
  hydroxyl group thus R-OH is the formula
  
• How is this different from the hydroxide ion?

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Alcohols

• Arranged into categories according to the number
  of R groups attached to the carbon with the
  hydroxyl
  
• 1 R group primary alcohol
• 2 R groups secondary alcohol
• 3 R groups tertiary alcohol
• Note drawings on page 778

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Alcohols

• Both IUPAC and common names
• For IUPAC
• drop the -e ending of the parent alkane name add
  ending of -ol, numbering the position of -OH
  
• parent is the longest chain that contains the
  carbon with the hydroxyl attached.

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Alcohols

• The hydroxyl is given the lowest position number
• Alcohols containing 2, 3, and 4 of the -OH
  substituents are named diols, triols, and tetrols
  respectively

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Alcohols

• Common names
• similar to halocarbons, meaning name the alkyl
  group followed by the word alcohol
  
• One carbon alcohol methyl alcohol

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Alcohols

• More than one -OH substituents are called glycols
  (ethylene glycol?)
  
• Examples on page 779
• Phenols - compounds in which a hydroxyl group is
  attached directly to an aromatic ring. Cresol is
  the common name of o, m, and p isomers of
  methylphenol

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Properties of Alcohols

• Much like water, alcohols are capable of hydrogen
  bonding between molecules
  
• this means they will boil at a higher temp. than
  alkanes and halocarbons with a comparable number
  of atoms

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Properties of Alcohols

• Alcohols are derivates of water the -OH comes
  from water, and thus are somewhat soluble
  
• Alcohols of up to 4 carbons are soluble in all
  proportions more than 4 carbons are usually less
  soluble, because?

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Properties of Alcohols

• Many aliphatic alcohols used in laboratories,
  clinics, and industry
  
• Isopropyl alcohol (2-propanol) is rubbing
  alcohol used as antiseptic, and a base for
  perfume, creams, lotions, and other cosmetics
  
• Ethylene glycol (1,2-ethanediol) - commonly sold
  as antifreeze

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Properties of Alcohols

• Glycerol (1,2,3-propanetriol) - used as a
  moistening agent in cosmetics, foods, and drugs
  also a component of fats and oils
  
• Ethyl alcohol (ethanol) used in the intoxicating
  beverages an important industrial solvent

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Properties of Alcohols

• Denatured alcohol- means it has been made
  poisonous by the addition of other chemicals,
  often methyl alcohol (methanol, or wood alcohol).
  As little as 10 mL of methanol has been known
  to cause permanent blindness, and 30 ml has
  resulted in death!!!

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Addition Reactions

• Carbon-carbon single bond is not easy to break
• In double bonded alkenes, it is easier to break a
  bond
  
• Addition reaction- substance is added at the
  double or triple bond location, after it is broken

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Addition Reactions

• Addition of water to an alkene is a hydration
  reaction - usually occurs with heat and an acid
  (such as HCl or H2SO4 acting as a catalyst)
  
• Note sample at bottom of page 781 for the
  formation of ethanol from ethene water

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Addition Reactions

• If a halogen is added in an addition reaction,
  the result is a halocarbon that is disubstituted
  - top page 782
  
• The addition of bromine is often used as a test
  for saturation - p.782
  
• Addition of a hydrogen halide?

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Addition Reactions

• Addition of hydrogen to produce an alkane is a
  hydrogenation reaction, which usually involves a
  catalyst such as Pt or Pd
  
• common application is the manufacture of
  margarine from unsaturated vegetable oils

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Addition Reactions

• The hydrogenation of a double bond is a reduction
  reaction, which in one sense is defined as the
  gain of H
  
• On page 782, ethene is reduced to ethane
  cyclohexene is reduced to cyclohexane

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Ethers

• A class of organic compounds in which oxygen is
  bonded to 2 carbon groups R-O-R is formula
  
• Naming? The two R groups are alphabetized, and
  followed by ether
  
• Two R groups the same? Use the prefix di-
  Examples on page 783

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Ethers

• Diethyl ether is the one commonly called just
  ether
  
• was the first reliable general anesthetic
• dangerous- highly flammable, also causing nausea
• ethers are fairly soluble in water
• Note the LINK on page 784

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Section 26.3Carbonyl Compounds

• OBJECTIVES
• Distinguish among the carbonyl groups of
  aldehydes, ketones, carboxylic acids, and esters

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Section 26.3Carbonyl Compounds

• OBJECTIVES
• Describe the reactions of compounds that contain
  the carbonyl functional group

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Aldehydes and Ketones

• Review
• alcohol has an oxygen bonded to a carbon group
  and a hydrogen
  
• ether has an oxygen bonded to two carbon groups
• An oxygen can also be bonded to a single carbon
  by a double bond

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Aldehydes and Ketones

• The CO group is called the carbonyl group
• it is the functional group in both aldehydes and
  ketones
  
• Aldehydes - carbonyl group always joined to at
  least one hydrogen (meaning it is always on the
  end!)

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Aldehydes and Ketones

• Ketones - the carbon of the carbonyl group is
  joined to two other carbons (meaning it is never
  on the end)
  
• Structures - middle of page 785

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Aldehydes and Ketones

• Naming?
• Aldehydes identify longest chain containing the
  carbonyl group, then the -e ending replaced by
  -al, such as methanal, ethanal, etc.
  
• ketones longest chain w/carbonyl, then new
  ending of -one number it
  
• propanone, 2-pentanone, 3-pentanone

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Aldehydes and Ketones

• Table 26.4, page 786 examples
• Neither can form intermolecular hydrogen bonds,
  thus a much lower b.p. than corresponding
  alcohols
  
• wide variety have been isolated from plants and
  animals possible fragrant odor or taste many
  common names

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Aldehydes and Ketones

• Benzaldehyde
• Cinnamaldehyde
• Vanillin
• Methanal (common formaldehyde)
• 40 in water is formalin, a preservative

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Aldehydes and Ketones

• Propanone (common acetone) is a good solvent
  miscible with water in all proportions
  
• why is it a good substance used in nail-polish
  removers?

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Carboxylic Acids

• Also have a carbonyl group (CO), but is also
  attached to a hydroxyl group (-OH) carboxyl
  group
  
• general formula R-COOH
• weak acids (ionize slightly)
• Named by replacing -e with -oic and followed by
  the word acid
  
• methanoic acid ethanoic acid

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Carboxylic Acids

• Abundant and widely distributed in nature, many
  having a Greek or Latin word describing their
  origin
  
• acetic acid from acetum, meaning vinegar
• many that were isolated from fats are called
  fatty acids
  
• Table 26.6 page 789

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Esters

• General formula RCOOR
• Derivatives of the carboxylic acids, in which the
  -OH from the carboxyl group is replaced by an -OR
  from an alcohol
  
• carboxylic acid alcohol ? ester water
• many esters have pleasant, fruity odors- banana,
  pineapple, perfumes

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Esters

• Although polar, they do not form hydrogen bonds
  (reason there is no hydrogen bonded to a highly
  electronegative atom)
  
• thus, much lower b.p. than the hydrogen-bonded
  carboxylic acids they came from!

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Esters

• Can be prepared from a carboxylic acid and an
  alcohol usually a trace of mineral acid added as
  catalyst (because acids are dehydrating agents)
  
• Note equation on bottom p. 790

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Esters

• Naming? It has 2 words
• 1st alkyl attached to single bonded oxygen from
  alcohol
  
• 2nd take the acid name, remove the -ic acid, add
  -ate
  
• example on top of page 791

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Oxidation- Reduction Reactions

• All of the previous classes of organic compounds
  are related by oxidation and reduction
  reactions.
  
• What is oxidation-reduction?
• Oxidation the gain of oxygen, loss of hydrogen,
  or loss of e-1
  
• Reduction the loss of oxygen, gain of hydrogen,
  or gain of e-1

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Oxidation- Reduction Reactions

• Oxidation and reduction reactions (sometimes
  called redox) are coupled- one does not occur
  without the other
  
• The number of O and H attached to C indicates the
  degree of oxidation

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Oxidation- Reduction Reactions

• The fewer the of H on a C-C bond, the more
  oxidized the bond.
  
• Thus, a triple bond is more oxidized than a
  double bond and a single bond
  
• An alkane is oxidized (loss of H) to an alkene,
  and then to an alkyne

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Oxidation- Reduction Reactions

• Loss of hydrogen is called a dehydrogenation
  reaction
  
• may require strong heating and a catalyst
• Note equations on page 791

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Oxidation- Reduction Reactions

• Methane can be oxidized in steps to carbon
  dioxide (top page 792)
  
• methane ? methanol ? methanal ? methanoic acid ?
  CO2
  
• the more reduced (more H) a carbon compound, the
  more energy it can release upon oxidation
  

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Oxidation- Reduction Reactions

• Alcohols can also be oxidized into other
  products
  
• Dr. Al K. Hall ? Mr. Al D. Hyde
• Equations top of page 793
• Preparing aldehydes this way is a problem,
  because they are then easily oxidized to
  carboxylic acids

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Oxidation- Reduction Reactions

• Benedicts test and Fehlings test are commonly
  used for aldehyde detection - margin p. 793

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Section 26.4Polymerization

• OBJECTIVES
• Define polymer and monomer

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Section 26.4Polymerization

• OBJECTIVES
• Name and describe the uses of some important
  addition and condensation polymers

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Addition Polymers

• Polymers are giant molecules, not small like the
  ones studied earlier in this chapter
  
• examples are plastics
• Polymer- large molecule formed by the covalent
  bonding of smaller molecules called monomers

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Addition Polymers

• An addition polymer forms when unsaturated
  monomers react to form a polymer
  
• ethene will form polyethylene, shown on page 795
• polyethylene is easy to clean, chemically
  resistant- milk bottles, plastic wrap,
  refrigerator dishes

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Addition Polymers

• Polypropylene is a stiffer polymer, used in
  utensils and containers
  
• Polystyrene is formed from styrene
  (phenylethene), and is a poor heat conductor
  
• molded coffee cups and picnic coolers, insulates
  homes
  
• Polyvinyl chloride (PVC) used for pipes in
  plumbing

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Addition Polymers

• Polytetrafluoroethene (PTFE, or Teflon) is very
  resistant to heat and chemical corrosion
  
• found on nonstick cookware coating on bearings
  and bushings used in chemical reactors

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Condensation Polymers

• Condensation polymers are formed by the
  head-to-tail joining of monomer units
  
• usually accompanied by the loss of water from the
  reacting monomers, and forming water as a product

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Condensation Polymers

• Ex polyethylene terephthalate (PET)
• Dacron?, Fortrel?, Polyesters permanent press
  clothing, tire cords
  
• Sheets of polyester called Mylar?, used as
  magnetic tape in tape recorders and computers, as
  well as balloons
  
• Nylon carpet, fishing line, hosiery

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Condensation Polymers

• Examples
• aromatic rings form Nomex?, which is a poor
  electrical conductor makes parts for electrical
  fixtures flame resistant clothing for race car
  drivers flame resistant building materials
• Kevlar? strong and flame resistant