Functional Groups

Chapter 23
“Functional Groups”
Pre-AP Chemistry
Charles Page High School
Stephen L. Cotton
Section 23.1 - Introduction to Functional Groups
OBJECTIVES:
Explain how organic compounds are classified.
Section 23.1 - Introduction to Functional Groups
OBJECTIVES:
Identify halocarbons and the IUPAC rules for naming halocarbons.
Section 23.1 - Introduction to Functional Groups
OBJECTIVES:
Describe how halocarbons can be prepared.
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
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.
Functional Groups
The symbol “R” is used to represent any carbon chains or rings
Important: Table 23.1, page 726 -- shows some of the major categories, and their functional groups - KNOW THESE.
Table 23.2, p. 727 - alkyl groups
Halogen Substituents
Halocarbons - class of organic compounds containing covalently bonded fluorine, chlorine, bromine, or iodine
General formula: R-X (X = halogen)
Naming? Name parent as normal, add the halogen as a substituent (or prefix) - Examples on page 726
Halogen Substituents
Common names…p.726
The more highly halogenated the compound is, the higher the b.p. (see Table 23.3, page 728)
Few halocarbons found in nature
but, readily prepared and used
halothane (Fig. 23.3, p.727) and also the hydrofluorocarbons
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
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
Substitution Reactions
Treating benzene with a halogen? Examples on Page 729
Halogens on carbon chains are readily displaced by hydroxide ions (OH1-) to make an alcohol + a salt:
R-X + OH1-  R-OH + X1-
CH3-Cl + NaOH  CH3-OH + NaCl
Methanol + sodium chloride
Substitution Reactions
CH3-I + KOH  CH3-OH + KI


CH3CH2Br + NaOH  CH3CH2OH + NaBr
Iodomethane
Methanol
Bromoethane
Ethanol
Section 23.2
Alcohols and Ethers
OBJECTIVES:
Identify how alcohols are classified and named.
Section 23.2
Alcohols and Ethers
OBJECTIVES:
Predict how the solubility of an alcohol varies with the length of its carbon chain.
Section 23.2
Alcohols and Ethers
OBJECTIVES:
Name the reactions of alkenes that may be used to introduce functional groups.
Section 23.2
Alcohols and Ethers
OBJECTIVES:
Construct the general structure of an ether and describe how ethers are named.
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? (covalent bonding with the carbon- not ionic with a metal like bases)
Alcohols
Aliphatic alcohols classified 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 730
Alcohols
Both IUPAC and common names
For IUPAC:
drop the -e ending of the parent alkane name; add ending of -ol, number the position of -OH
parent is the longest chain that contains the carbon with the hydroxyl attached.
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
Examples on page 731
Alcohols
Common names:
similar to halocarbons, meaning name the alkyl group, then followed by the word alcohol
One carbon alcohol = methyl alcohol
Alcohols
More than one -OH substituents are called glycols (ethylene glycol?)
** Examples on page 731 **
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
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
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 water in all proportions; more than 4 carbons are usually less soluble, because the longer carbon chain is more nonpolar
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”
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; also an important industrial solvent
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!
Addition Reactions
The 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
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 top of page 734 for the formation of ethanol from ethene + water
Addition Reactions
If a halogen is added in an addition reaction, the result is a halocarbon that is disubstituted - middle p. 734
The addition of bromine is often used as a test for saturation - p.734
Addition of a hydrogen halide? -called monosubstituted halocarbon
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 (making them solid from a liquid)
Addition Reactions
The hydrogenation of a double bond is a reduction reaction, which in one sense is defined as the “gain of H”
Top- page 735, ethene is “reduced” to ethane; cyclohexene is “reduced” to cyclohexane
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 735
Ethers
Diethyl ether is the one commonly called just “ether”
was the first reliable general anesthetic
dangerous- highly flammable, also causes nausea
ethers are fairly soluble in water
Alcohol used for fuel in the future?
Section 23.3
Carbonyl Compounds
OBJECTIVES:
Identify the structure of a carbonyl group as found in aldehydes and ketones.
Section 23.3
Carbonyl Compounds
OBJECTIVES:
Construct the general formula for carboxylic acids and explain how they are named.
Section 23.3
Carbonyl Compounds
OBJECTIVES:
Describe an ester.
Section 23.3
Carbonyl Compounds
OBJECTIVES:
Explain how dehydrogenation is an oxidation reaction.
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
Aldehydes and Ketones
The C=O 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!)
Aldehydes and Ketones
Ketones - the carbon of the carbonyl group is joined to two other carbons (meaning it is never on the end)
Structures - bottom of page 737
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
Aldehydes and Ketones
Table 23.4, page 738 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
Aldehydes and Ketones
Benzaldehyde
Cinnamaldehyde
Vanillin
Methanal (the common name is: formaldehyde)
40% in water is formalin, a preservative
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? (a powerful solvent-able to dissolve both polar & nonpolar)
The Carboxylic Acids…
Also have a carbonyl group (C=O), 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
Carboxylic Acids
Abundant and widely distributed in nature, many having a Greek or Latin word describing their origin
acetic acid (ethanoic acid) from acetum, meaning vinegar
many that were isolated from fats are called fatty acids
Table 23.6 page 741
The 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
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
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. 742
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 743
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
Oxidation- Reduction Reactions
Oxidation and reduction reactions (sometimes called redox) are coupled- one does not occur without the other
The number of Oxygen and Hydrogen attached to Carbon indicates the degree of oxidation
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
Oxidation- Reduction Reactions
Loss of hydrogen is called a dehydrogenation reaction
may require strong heating and a catalyst
Note equations at the top on page 744
Oxidation- Reduction Reactions
Methane can be oxidized in steps to carbon dioxide (middle p. 744):
methane  methanol  methanal  methanoic acid  CO2
the more reduced (more H) a carbon compound, the more energy it can release upon oxidation
Oxidation- Reduction Reactions
Alcohols can also be oxidized into other products
“Dr. Al K. Hall  Mr. Al D. Hyde”
Equations middle of page 745
Preparing aldehydes from a primary alcohol is a problem, because they are then easily oxidized to carboxylic acids
Oxidation- Reduction Reactions
Benedict’s test and Fehling’s test are commonly used for aldehyde detection – Figure 23.19 p. 745
Section 23.4
Polymerization
OBJECTIVES:
Describe how addition polymers are formed.
Section 23.4
Polymerization
OBJECTIVES:
Describe how condensation polymers are formed.
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
Polymers from Monomers
Addition Polymers
An addition polymer forms when unsaturated monomers react to form a polymer
ethene will form polyethylene, shown on page 747
polyethylene is easy to clean, chemically resistant- milk bottles, plastic wrap, refrigerator dishes
High Density Polyethylene
Addition Polymers
Polypropylene is a stiffer polymer, used in utensils and containers
Polystyrene is formed from styrene (phenylethene), and is a poor heat conductor (styrofoam ® Dow Chemical)
molded coffee cups and picnic coolers, insulates homes
Polyvinyl chloride (PVC) used for pipes in plumbing
Addition Polymers
Polytetrafluoroethene (PTFE, or teflon ® DuPont) is very resistant to heat and chemical corrosion
found on nonstick cookware; coating on bearings and bushings used in chemical reactors
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
Condensation Polymers
Ex: polyethylene terephthalate (PET)
Dacron (® DuPont), Fortrel (® Wellman), Polyesters: permanent press clothing, tire cords
Sheets of polyester called Mylar (® DuPont), used as magnetic tape in tape recorders and computers, as well as balloons
Nylon: carpet, fishing line, hosiery
Condensation Polymers
Examples:
aromatic rings form Nomex (® DuPont), which is a poor electrical conductor; makes parts for electrical fixtures; flame resistant clothing for race car drivers; flame resistant building materials
Kevlar (® DuPont): strong and flame resistant
Plastic container code system.
What Do the Numbers Mean?
1 -- PETE (Polyethylene terephthalate)
PET (or PETE) is used in the production of soft drink bottles, peanut butter jars...
PET can be recycled into fiberfill for sleeping bags, carpet fibers, rope, pillows...
What Do the Numbers Mean?
2 -- HDPE (High-density polyethylene)
HDPE is found in milk jugs, butter tubs, detergent bottles, motor oil bottles...
HDPE can be recycled into flower pots, trash cans, traffic barrier cones, detergent bottles...
What Do the Numbers Mean?
3 -- V (Polyvinyl chloride)
PVC is used in shampoo bottles, cooking oil bottles, fast food service items...
PVC can be recycled into drainage and irrigation pipes...
What Do the Numbers Mean?
4 -- LDPE (Low-density polyethylene)
LDPE is found in grocery bags, bread bags, shrink wrap, margarine tub tops...
LDPE can be recycled into new grocery bags...
What Do the Numbers Mean?
5 -- PP (Polypropylene)
PP is used in most yogurt containers, straws, pancake syrup bottles, bottle caps....
PP can be recycled into plastic lumber, car battery cases, manhole steps...
What Do the Numbers Mean?
6 -- PS (Polystyrene)
PS is found in disposable hot cups, packaging materials (peanuts), and meat trays...
PS can be recycled into plastic lumber, cassette tape boxes, flower pots...
What Do the Numbers Mean?
7 -- Other
This is usually a mixture of various plastics, like squeeze ketchup bottles, "microwaveable" dishes...
Timeline of Plastics
1862 – First man-made plastic
1866 – Celluloid makes it’s debut
1891 – Rayon is discovered
1907 – Bakelite is invented
1913 – Cellophane causes the plastics craze
Timeline of Plastics
1926 – PVC is invented
1933 – Polyethylene is discovered
1933 – Saran makes it’s debut
1938 – Teflon is discovered
1939 – Nylon stockings hit market
1957 – Here comes velcro
End of Chapter 23