chapter 23 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.


OBJECTIVES:

–Identify halocarbons and the IUPAC rules for naming halocarbons.


OBJECTIVES:

–Describe how halocarbons can be prepared.

Functional GroupsMost 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 23.1, page 726 -- shows some of the major categories, and their functional groups - KNOW THESE.

Table 23.2, p. 727 - alkyl groups

Halogen SubstituentsHalocarbons - 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 ReactionsOrganic reactions often much

slowerslower 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?

Examples on Page 729Halogens 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 + NaClMethanol + sodium chloride

Substitution Reactions

CH3-I + KOH CH3-OH + KI

CH3CH2Br + NaOH CH3CH2OH + NaBr

Iodomethane Methanol

Bromoethane Ethanol

Section 23.2Alcohols and Ethers

OBJECTIVES:

–Identify how alcohols are classified and named.


OBJECTIVES:

–Predict how the solubility of an alcohol varies with the length of its carbon chain.


OBJECTIVES:

–Name the reactions of alkenes that may be used to introduce functional groups.


OBJECTIVES:

–Construct the general structure of an ether and describe how ethers are named.

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 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.

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 731

AlcoholsCommon 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 AlcoholsGlycerol (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 AlcoholsDenatured 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 23.3Carbonyl Compounds

OBJECTIVES:

–Identify the structure of a carbonyl group as found in aldehydes and ketones.


OBJECTIVES:

–Construct the general formula for carboxylic acids and explain how they are named.


OBJECTIVES:

–Describe an ester.


OBJECTIVES:

–Explain how dehydrogenation is an oxidation reaction.

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 KetonesKetones - 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 KetonesBenzaldehydeCinnamaldehydeVanillinMethanal (the common name is:

formaldehyde)–40% in water is formalin, a

preservative

Aldehydes and KetonesPropanone (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

EstersAlthough 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

EstersCan 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

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 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 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 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 ReactionsAlcohols can also be oxidized

into other products “Dr. Al K. Hall Mr. Al D. Hyde”Equations middle of page 745Preparing aldehydes from a

primary 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 – Figure 23.19 p. 745

Section 23.4Polymerization

OBJECTIVES:

–Describe how addition polymers are formed.

Section 23.4Polymerization

OBJECTIVES:

–Describe how condensation polymers are formed.

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 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 PolymersPolytetrafluoroethene (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 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 (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.

CODE MATERIALPERCENT OF

TOTAL

Polyethylene Terephthalate

(PET)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 (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...


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

chapter 23 functional groups

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