Chapter 26 “Functional Groups and Organic Reactions”

Chapter 26“Functional Groups and

Organic Reactions”

Charles Page High SchoolDr. Stephen L. Cotton

Section 26.1 - Introduction to Functional Groups

OBJECTIVES:–Define a functional group, and

give several examples.

Section 26.1 - Introduction to Functional Groups

OBJECTIVES:–Describe halocarbons, and

the substitution reactions they undergo.

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 GroupsFunctional 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 GroupsThe 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 - KNOW THESE.

Table 26.2, p. 775 - alkyl groups

Halogen SubstituentsHalocarbons - class of organic

compounds containing covalently bonded fluorine, chlorine, bromine, or iodine–General formula: R-X

Naming? Name parent as normal, add the halogen as a substituent (or prefix) - Examples on page 774

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

Substitution ReactionsOrganic 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 + HClUV light

Substitution ReactionsTreating benzene with a halogen?

Page 776Halogens 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

Substitution Reactions

CH3-I + KOH CH3-OH + KI

CH3CH2Br + NaOH CH3CH2OH + NaBr

Iodomethane Methanol

Bromoethane Ethanol

Section 26.2Alcohols and Ethers

OBJECTIVES:–Describe the structures and

naming of alcohols and ethers.


OBJECTIVES:–Define an addition reaction,

and give several examples.


OBJECTIVES:–Compare the properties of

alcohols and ethers.

AlcoholsAlcohols - 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 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

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.

AlcoholsThe hydroxyl is given the

lowest position numberAlcohols containing 2, 3, and 4

of the -OH substituents are named diols, triols, and tetrols respectively–Examples on page 779

AlcoholsCommon names:

–similar to halocarbons, meaning name the alkyl group followed by the word alcohol

–One carbon alcohol = methyl alcohol

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

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


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…?

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


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

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

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 bottom of page 781 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 - top page 782

The addition of bromine is often used as a test for saturation - p.782

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

Bottom- page 782, 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 783

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 Note the LINK on page 784

Section 26.3Carbonyl Compounds

OBJECTIVES:–Distinguish among the

carbonyl groups of aldehydes, ketones, carboxylic acids, and esters.

Section 26.3Carbonyl Compounds

OBJECTIVES:–Describe the reactions of

compounds that contain the carbonyl functional group.

Aldehydes and KetonesReview:

–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 - middle of page 785

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


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


Benzaldehyde Cinnamaldehyde Vanillin Methanal (common: formaldehyde)

–40% in water is formalin, a preservative


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)

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

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. 790

EstersNaming? 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

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 ReactionsOxidation 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


Loss of hydrogen is called a dehydrogenation reaction–may require strong heating

and a catalystNote equations on page 791

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

Oxidation- Reduction ReactionsAlcohols can also be oxidized

into other products “Dr. Al K. Hall Mr. Al D. Hyde”Equations top of page 793Preparing aldehydes from a

primaryf alcohol is a problem, because they are then easily oxidized to carboxylic acids


Benedict’s test and Fehling’s test are commonly used for aldehyde detection - margin p. 793

Section 26.4Polymerization

OBJECTIVES:–Define polymer and monomer.

Section 26.4Polymerization

OBJECTIVES:–Name and describe the uses

of some important addition and condensation polymers.

Addition PolymersPolymers 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 PolymersAn 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

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 PolymersPolytetrafluoroethene (PTFE, or

“Teflon”) is very resistant to heat and chemical corrosion–found on nonstick cookware;

coating on bearings and bushings used in chemical reactors

Condensation PolymersCondensation 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 (PETE)

–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

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

Plastic container code system.

CODE MATERIAL PERCENT OF TOTAL

Polyethylene Terephthalate (PETE) 20-30 percent

High Density Polyethylene 50-60 percent

Polyvinyl Chloride (PVC) 5-10 percent

Low Density Polyethylene 5-10 percent

Polypropylene 5-10 percent Polystyrene 5-10 percent All other resins 5-10 percent

What Do the Numbers Mean?1 -- PETE (Polyethylene terephthalate)

•PET 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...


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...


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...


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...


7 -- Other•This is usually a mixture of various plastics, like squeeze ketchup bottles, "microwaveable" dishes...

Timeline of Plastics1862 – 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 Plastics1926 – 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

Documents

Chapter 26 “Functional Groups and Organic Reactions”