Chemistry 102 Demonstrations

Winter Quarter 2002

Large ball-and-stick models or large plastic Darling models of hydrocarbons and cyclic compounds with or without substituents and various functional groups can be constructed upon request.

Chapter 13 - The Organization of Organic Chemistry

a) Organic Compounds

1) To show how organic compounds permeate daily life, display various food and/or toiletry packages and read the list of ingredients, pointing out the organic compounds

2) You may wish to show the 29 minute World of Chemistry video "Carbon" (UTS #3614); University Technology Services requires a MINIMUM of 48 hours notice.

3) Show ball-and-stick models of butane and cyclobutane to highlight carbon's ability to form chains or rings of atoms

b) Bonding and Molecular Shapes

1) Use a lucite tetrahedron containing a ball-and-stick model of CH₄ to clearly illustrate the tetrahedral geometry of carbon in CH₄

2) Use balloons or ball-and-stick models to show sp³, sp², and sp geometry around a central carbon atom

3) Bring pairs of orbitals close together (such as s and s, s and p, s and a hybrid orbital, two p's end-to-end, and finally two parallel p's) to show how sigma and pi bonds are formed

4) Show orbital overlap models and ball-and-stick models of ethane, ethylene, and acetylene (and/or formaldehyde) to illustrate formation of sigma and pi bonds

c) Structural Formulas and Conformations

1) Show ball-and-stick models of simple alkanes; small space-filling models of the same alkanes can be provided also, if desired

2) Show a large model of NaCl to remind students of the structural differences between ionic and covalent compounds

3) Show a space-filling model of a larger alkane (such as a branched heptane) or a more elaborate

compound such as cholesterol (subject to availability from Martin Caffrey)

4) Use duplicate models of ethane, propane, or butane to show various conformers

5) Use duplicate models of ethane or 1,2-difluoroethane to contrast staggered and eclipsed conformations

d) Isomers - show models of isomers

1) Contrast models of butane and isobutane, butanol and isobutanol, and/or ethanol and dimethyl ether

2) Contrast models of 1-chloropropane and 2-chloropropane

3) Contrast models of 1,1-dichloroethane and 1,2-dichloroethane

4) Contrast models of two dibromopropanes or dibromobutanes to determine whether they are conformers or isomers

e) Acid-Base Reactions in Organic Chemistry

1) If you want to review the Bronsted-Lowry theory of acids as proton donors, toss a racquet ball labeled H⁺ to a student, then hold up your hand so the student throws it back; now ask "Do you know what you've done? . . .You've made an acid of yourself!"

2) To introduce Lewis theory, continue the racquet ball analogy from 1 above, this time using a ball labeled with an electron pair; whoever tosses this ball makes an acid of the person who catches it, as that person becomes an electron pair acceptor

Chapter 14 - Alkanes and Cycloalkanes

a) Classes of Hydrocarbons - show models of butane and cyclobutane to introduce alkanes and cycloalkanes

b) Alkanes

1) Normal Alkanes - start with a model of CH₄ and add -CH₂- units to show the build-up of a homologous series

2) Branched Alkanes - remove a hydrogen atom from an internal carbon atom on an alkane model and replace it with -CH₃ to illustrate a branched-chain alkane

3) Show models of normal and branched isomers (e.g., n-pentane, isopentane, and neopentane)

4) Classification of Carbon Atoms - use models of ethane, propane, and 2-methylpropane to point out primary, secondary, and tertiary carbon atoms. (You may request that different colored balls be used for 2^o and 3^o carbon atoms, if desired.)

c) Nomenclature of Alkanes

1) Use a model of a branched alkane such as 2-methylbutane or 2,4-dimethylheptane to introduce nomenclature

2) Names of Alkyl Groups - starting with models of propane, normal butane, and/or isobutane, remove different hydrogen atoms to show the formation of various alkyl groups

d) Cycloalkanes

1) Show models of cyclopropane, cyclobutane, cyclopentane, and cyclohexane

2) Display an extra large model of cyclohexane (60-80 cm across, large enough to "stand inside")

3) Show two models of cyclohexane to contrast the chair and boat conformations

4) Pass around large plastic Darling models of cyclohexane so students can appreciate its unique structure and contrast the chair and boat conformations for themselves

5) Add colored substituents to two models of a cycloalkane to show cis and trans isomers

6) If you wish to define the terms axial and equatorial, show two cyclohexane models with colored substituents (one color for axial, another color for equatorial)

7) Show a large plastic Darling model of adamantane, as seen in Example 14.5 in the text

8) Show a space-filling model of cholesterol (subject to availability from Martin Caffrey) to introduce students to the multiple ring structure common in steroids

e) Physical Properties of Saturated Hydrocarbons

1) Mix hexane and colored water in a beaker to demonstrate both the insolubility of

an alkane in water and its low density

2) Use two models of methane and two models of butane or pentane to show how a higher molecular weight increases London forces with a resulting increase in boiling point

3) Use two models of pentane and two models of neopentane to demonstrate how branching decreases London forces with a resulting decrease in boiling point

4) Use pairs of ball-and-stick models or space-filling models of the pentane isomers to show that increased branching increases compactness, decreases polarizability, and decreases London forces with a resulting decrease in boiling point

f) Oxidation of Alkanes and Cycloalkanes

1) Show the oxidation of methane by igniting large soap bubbles filled with CH₄ with a candle on a dowel rod - the result is very impressive!

2) You may wish to contrast combustion of methane bubbles with combustion of a 2:1 ratio of oxygen and methane in a balloon - the sight and sound of the two methods of combustion are very different (due to the effect of concentration on reaction rate)

3) Burn a small amount of heptane or octane in a watchglass

g) Halogenation of Saturated Hydrocarbons - show ball-and-stick models of mono-, di-, tri-, and tetrachlorinated methane and/or ethane

Chapter 15 - Unsaturated Hydrocarbons

a) Types of Unsaturated Hydrocarbons - you may wish to contrast the following models with an orbital overlap model and a ball-and-stick model of ethane

1) Alkenes - show an orbital overlap model and a ball-and-stick model of ethylene

2) Alkynes - show an orbital overlap model and a ball-and-stick model of acetylene

b) Geometric Isomerism

1) Contrast models of 1,2-dichloroethane, cis-1,2-dichloroethylene, trans-1,2-dichloroethylene, and 1,1-dichloroethylene

2) Contrast models of butane, 1-butene, cis-2-butene, and trans-2-butene

c) Oxidation and Reduction of Alkenes - on the overhead projector, demonstrate the reaction of KMnO₄ with an alkene, and also show that KMnO₄ does not react with an alkane

d) Addition Reactions of Alkenes

1) Add chlorine water to tomato juice: Cl₂ adds across the double bonds in carotene (p. 355 in the text), destroying the conjugated system and completely decolorizing the tomato juice

2) On the overhead projector, add an alkane and an alkene to solutions of Br₂ in 1,4-dioxane to show that Br₂ adds to the alkene but not the alkane

3) Display models of propene and the two compounds that might result from addition of HCl to propane: 1-chloropropane and 2-chloropropane

e) Polymerization of Alkenes

1) Make a styrofoam (expanded polystyrene) cup "disappear" by placing it in a dish of acetone

2) See how much water you can add to a disposable diaper containing the super-absorbent powder, Water Lock J-550, which is polysodium acrylate cross-linked with starch; the original polymer results from multiple addition reactions of the alkene functional groups of acrylic acid molecules. (One diaper holds 1 L of water!)

3) You may wish to show the 29-minute World of Chemistry Video "The Age of Polymers" (UTS #3614-2nd program); UTS requires a MINIMUM of 48 hours notice

f) Reactions of Alkynes - show the preparation of acetylene by adding calcium carbide to water, followed by the explosive combustion of acetylene as the escaping gas is ignited

g) Aromatic Hydrocarbons

1) Contrast two styrofoam models of benzene, one showing sp² orbitals and p orbitals and one (somewhat damaged) showing delocalization over the whole ring, and a ball-and-stick model showing three pi bonds

2) Pass plastic models of benzene around the class so the students can observe its symmetrical planar structure and sp² bond angles

3) Add colored substituents to three large plastic Darling models of benzene to show ortho, meta, and para substitution

4) On the overhead projector, add cyclohexene and toluene to separate samples of Br₂ in 1,4-dioxane to show that aromatic rings don't undergo addition reactions like alkenes do

h) Polycyclic Aromatic Hydrocarbons

1) Show a model of naphthalene; pass models around the class if desired

2) Display a box of naphthalene moth flakes and pass samples around the class for the students to smell

3) Show a large plastic Darling model of anthracene and/or phenanthrene

Chapter 16 - Alcohols, Phenols, and Ethers

a) Compounds of Oxygen

1) Show ball-and-stick models of water, methanol, phenol, and dimethyl ether OR show the relationship of alcohols and ethers to water by replacing -H on the water model with methyl or phenyl groups

2) Contrast the reaction of sodium and water with the reaction of sodium and various alcohols (this is shown in the video for Experiment 27, but could be done in class too)

b) Common Alcohols and Phenols - display bottles or cans of familiar products containing alcohols or phenols: windshield washer fluid (methanol), wine or beer (ethanol), rubbing alcohol (isopropyl alcohol), antifreeze (ethylene glycol), skin lotion (glycerol), Lysol (cresols)

c) Nomenclature and Classification of Alcohols - show models of simple 1°, 2°, and 3° alcohols (e.g., ethanol, 1-propanol, 2-propanol, 2-methyl-2-propanol)

d) Hydrogen Bonding in Alcohols

1) Demonstrate the negative volume of mixing for ethanol and water using a special sealed tube to show one result of intermolecular hydrogen bonding

2) Ask the class to predict which compound in each of three pairs of liquids (ethanol and butanol, butanol and tert-butanol, butanol and diethyl ether) will evaporate first when students make streaks of each on the blackboard; the class must consider differences in London forces, branching, and hydrogen bonding (or lack of it) in making their predictions

3) Mix ethanol and colored water in one beaker and mix octanol and colored water in another beaker to contrast miscibility and immiscibility due to differences in the intermolecular forces of alcohols as the size of the alkyl group increases. (You may also wish to mix diethyl ether and colored water in a third beaker.)

e) Acid-Base Reactions

1) Contrast the addition of phenolphthalein to NaOH(aq) and to an alcohol to show that no free OH- is present in an alcohol

2) Acidity of Phenols - use a separatory funnel to demonstrate the acidity and base-solubility of a phenol, indophenol, which is red and ether-soluble and can be converted to its sodium salt, which is blue and water-soluble, by adding NaOH: the indophenol can be restored to the red ether-soluble form by adding HCl

f) Substitution Reactions - contrast the responses of 1°, 2°, and 3° alcohols to the Lucas reagent (HCl/ZnCl₂); note that this demonstration requires adequate ventilation, preferably a hood

g) Oxidation of Alcohols

1) Combine saturated calcium acetate and ethanol to produce "Sterno", then ignite the gel to demonstrate the use of alcohols in fuels

2) Money to burn - soak a dollar bill in a 50:50 mixture of 2-propanol and water, then ignite it - the alcohol will burn without damaging the bill due to the high heat capacity of water

3) Combustion of ethanol - allow a small amount of ethanol to vaporize in a gallon milk carton, pour out the excess liquid, then hold a lighted splint to the mouth of the milk carton - the flamboyant reaction also demonstrates the flammability of organic vapors

4) Combustion of methanol - allow a small amount of methanol to vaporize in a large plastic carboy (subject to availability), then hold a lighted splint to the mouth of the carboy for a dramatic demonstration of the flammability of organic vapors

5) Oxidation of 1^o, 2^o, and 3^o Alcohols with K₂Cr₂O₇ - perform this demonstration on the overhead projector or in flasks; the 1^o and 2^o alcohol solutions change from orange to green to blue [as the Cr(VI) is reduced], while the 3^o alcohol does not react; this reaction is the basis for the Breathalyzer test

h) Ethers - demonstrate the high vapor pressure and flammability of diethyl ether by allowing the vapor to flow from a can down a trough to a candle, resulting in a vapor flashback fire

i) Sulfur Compounds - show a model of mercaptoethanol (ethanethiol) and pass around small samples of the compound for the students to smell

j) Polyvinyl Alcohol Slime - mix solutions of polyvinyl alcohol and borax to make "Slime", a cross-linked gel; use this demonstration to relate concepts such as polymers and hydrogen-bonding to a commercial product students are familiar with

Chapter 17 - Aldehydes and Ketones

a) The Carbonyl Group - show models of formaldehyde, acetaldehyde, and acetone

b) Physical Properties of Aldehydes and Ketones - pass around samples of various aldehydes and ketones for students to smell, and show the structures so the class can identify the functional groups; examples of aldehydes and ketones used in flavorings and/or perfumery include cinnamaldehyde, benzaldehyde (almond), vanillin, (S)-(+)-carvone (caraway), and (R)-(-)-carvone (spearmint)

c) Oxidation of Carbonyl Compounds

1) Use Tollens' reagent and an aldehyde to silver a small Erlenmeyer flask

2) Use Benedict's solution and dextrose to demonstrate Benedict's test for aldehydes

d) Addition Reactions of Carbonyl Compounds

1) Addition of Oxygen Compounds - use a flexible open-chain model of glucose and a large plastic cyclic model of glucose to show how the C-5 hydroxyl group can react with the C-1 carbonyl group, resulting in cyclization to form the hemiacetal

2) Addition of Nitrogen Compounds

A) Add base to a mixture of 2,3-butanedione and methylamine hydrochloride to produce an imine with a strong pleasant aroma of corn chips (subject to availability of reagents)

B) Use 2,4-dinitrophenylhydrazine and acetone, cyclohexanone, or benzaldehyde to show formation of the 2,4-DNP product

e) Reactivity of the a-Carbon Atom - show models of the keto and enol forms of acetone; remove an H atom from each model to show the two resonance forms of the conjugate base

f) The Aldol Condensation - show the reaction between acetone and cinnamaldehyde in base, which results in a mixed aldol condensation that produces a yellow precipitate

Chapter 18 - Carboxylic Acids and Esters

a) Carboxylic Acids and Derivatives

1) Show models of formic acid and acetic acid; extra -CH₂- units can be provided if you wish to expand acetic acid to show propionic or butyric acid

2) Show large Darling models of benzoic acid and, if desired, p-bromobenzoic acid

3) Show large Darling models of maleic acid and fumaric acid

4) Show models of selected acid derivatives and/or polyfunctional carboxylic acids, such as lactic acid and pyruvic acid

5) Add conc. H₂SO₄ to formic acid to produce H₂O and CO(g), then ignite the CO(g) to show that it burns with a blue flame

b) Physical Properties of Carboxylic Acids

1) Pass around samples of benzaldehyde and benzoic acid, so students can compare the odors

2) Pass around samples of selected acids, such as formic, acetic, pentanoic, and stearic, so students can compare the various odors

3) Show a model of a carboxylic acid dimer when discussing the high boiling points of carboxylic acids

c) Acidity of Carboxylic Acids - compare the acidity of acetic acid and dichloroacetic acid, using a pH meter or an indicator

d) Salts of Carboxylic Acids

1) Demonstrate the conversion of water-insoluble p-chlorobenzoic acid to its soluble salt and reconversion to the acid by adding first NaOH, then HCl

2) Demonstrate the oxidation of luminol, a chemiluminescent reaction which generates a beautiful blue light; the light-emitting species is the dicarboxylate ion, aminophthalate, the product of the oxidation

e) Esters

1) Contrast models of acetic acid and methyl acetate

2) Let the students experience the dramatic change in odor when an acid is esterified:

A) Pass around small samples of acetic acid, amyl acetate (banana), and octyl acetate (orange)

B) Pass around small samples of butyric acid, methyl butyrate (apple), and ethyl butyrate (pineapple)

3) Pass around small samples of amyl acetate (banana), octyl acetate (orange), methyl butyrate (apple), and ethyl butyrate (pineapple) so the students can compare the smells of different esters used as flavoring agents

4) Pour small samples of one or two of the esters listed in e3 into warm water to vaporize the samples so students throughout the room can smell them

Chapter 19 - Amines and Amides

a) Organic Nitrogen Compounds - show models of methylamine, acetamide, and acetonitrile

b) Structure and Classification of Amines

1) Show models of ammonia, methylamine, and trimethylamine; a brass rod representing the lone pair on nitrogen can be included if desired

2) Show a model of ammonia, then substitute a methyl group for each hydrogen atom one by one to illustrate 1^o, 2^o, and 3^o amines

3) Show models of methyl-, dimethyl-, and trimethylamine to illustrate 1^o, 2^o, and 3^o amines; also show a model of tert-butylamine to contrast the 3^o amine with the 3^o carbon atom in tert-butylamine. If desired, you may also display a model of a secondary or tertiary alcohol.

c) Basicity of Amines

1) Add an amine to an indicator solution to demonstrate its basicity

2) Show ball-and-stick models of the methylammonium ion and the tetramethylammonium ion

3) Demonstrate the conversion of water-insoluble p-chloroaniline to its soluble salt and reconversion to the base by adding first HCl, then NaOH. (Note: This demonstration is a bit slow and not very interesting, especially if you have already done the demonstration in Chapter 18, d1.)

d) Adrenaline - have two assistants in the back of the room unexpectedly pop several balloons to demonstrate the body's "fright response", the release into the bloodstream of the 2^o amine adrenaline (epinephrine, pages 458 and 465 in the text)

e) Amides

1) Show models of formamide and acetamide

2) Show models of the two resonance forms of formamide or the three resonance forms of

N-methylformamide (two of which are geometric isomers)

f) Formation of Amides

1) Show models of acetic acid and NH₃, the reactants used to produce acetamide

2) Nylon-a Polyamide - demonstrate the polymerization of hexamethylenediamine with sebacoyl chloride to produce the polyamide, Nylon 6-10

Chapter 20 - The Organization of Biochemistry

a) The Eukaryotic Cell - you may wish to show a 20 minute movie, "The Living Cell" (UTS #1474) which introduces the various structures and biochemical processes in living cells; UTS requires a MINIMUM of 48 hours notice

b) Mirror Images and Chirality - demonstrate the concept of "handedness" or chirality with your own hands and then with a pair of large thermal gloves

c) Molecular Chirality

1) Pass out sets of four different colored balls and a tetrahedral carbon to several students and ask them to construct CHXYZ, then compare their models - some will be identical, but hopefully you will get the enantiomer also

2) Construct models of mirror images of a molecule such as CHBrClF by substituting different colored balls for H atoms on two methane models, producing non-superimposable mirror images when the third H is substituted (square planar models can also be provided, if requested, to show that tetrahedral geometry is required for stereoisomerism)

3) Use a large mirror and a pair of enantiomeric models (CHBrClF) to explain the concept of non-superimposable mirror images; then you may wish to substitute a second Br for the Cl or F on each model to show that the chirality is lost

4) Show two models of CH₄, two models of CH₃Cl, two models of CH₂Cl₂, two models of CH₂ClBr, and an enantiomeric pair of CHBrClF models to contrast superimposable and nonsuperimposable mirror images; you can also point out the planes of symmetry that exist in all the models except CHBrClF, as shown in Figure 20.7 in the text

d) Optical Activity

1) Use a large model of a polarimeter to introduce the concept of plane-polarized light and later to explain how a polarimeter works

2) Use two large polaroid filters on the overhead projector to illustrate the concept of plane-polarized light

3) Place small beakers of (R)-(+)-limonene and (S)-(-)-limonene between two polaroid sheets on the overhead projector to show the equal but opposite rotation of plane-polarized light by these enantiomers; you can also show that a racemic mixture does not rotate polarized light

e) Fischer Projection Formulas

1) Use a model of CHXYZ as a visual aid in writing its Fischer projection formula; the enantiomer can also be provided to show that its Fischer projection formula is different. (If desired, a "flattened" model of CHXYZ can also be provided to represent the Fischer projection.)

2) Show large plastic Darling models of D-(+)- and L-(-)-glyceraldehyde

f) Multiple Chiral Centers

1) Show models of a pair of enantiomers with two stereogenic centers, then show models of a second pair of enantiomers which are diastereomers of the first pair

2) Show models of 2,3-dichlorobutane or tartaric acid, each of which has three stereoisomers: a pair of enantiomers and a diastereomeric meso form

3) Show two models of cis-1,2-dichlorocyclopropane and models of the enantiomeric pair of trans-1,2-dichlorocyclopropanes

g) Chirality and the Senses - pass samples of (S)-(+)-carvone (odor of caraway) and

(R)-(-)-carvone (odor of spearmint) around the class so students can experience the

dramatic difference in the odors of these enantiomers

Chapter 21 - Carbohydrates

a) Configuration of Monosaccharides - show a flexible open-chain model of glucose

b) Cyclic Forms of Monosaccharides - contrast a flexible open-chain model of glucose with large plastic Darling models of the cyclic forms of β-D-glucopyranose and β-D-fructofuranose

c) Oxidation of Carbohydrates

1) Drop an M&M into hot molten KClO₃ for a dramatic oxidation of sucrose; contrast this with the less dramatic oxidation that occurs when you eat an M&M

2) You may wish to perform Benedict's test as a demonstration, although the students will do the test in Experiment 32

d) Disaccharides

1) Display a large plastic Darling model of sucrose

2) Dehydration of Sucrose - add conc. H₂SO₄ to sugar in a tall-form beaker to produce a black column of carbon that grows out the top of the beaker. (NOTE: This demonstration is not suitable for classrooms without a fume hood, although a modified version is possible.)

Chapter 22 - Lipids

a) Terpenes - pass samples of limonene (both enantiomers are found in citrus oils), (S)-(+)-carvone (oil of caraway), and (R)-(-)-carvone (oil of spearmint) around the class so students can appreciate some of the distinctive odors of terpenes

b) Steroids - show a space-filling model of cholesterol (subject to availability from Martin Caffrey)

c) Fatty Acids - contrast space-filling models of a saturated fatty acid and an unsaturated fatty acid (subject to availability from Martin Caffrey)

d) Glycerophospholipids - show a space-filling model of a phosphoglyceride (subject to availability from Martin Caffrey)

e) Biological Membranes

1) To help develop the concept of a membrane, touch a wood applicator dipped in detergent to a film of talcum powder in a large crystallizing dish on the overhead projector; the detergent instantaneously spreads out to form a monolayer, pushing the talc to the sides

2) Show a transparency depicting the lipid bilayer and integral proteins in a biological membrane as in Figure 22.10

Chapter 23 - Amino Acids and Proteins

a) The Biological Role of Proteins - to show the function of the structural protein collagen, contrast a regular turkey drumstick with a "rubberized" turkey drumstick from which Ca₃(PO₄)₂ and other minerals have been dissolved, subject to availability

b) Amino Acids - show models of simple amino acids such as glycine and alanine

c) Structure of Proteins

1) You may wish to show the 29 minute World of Chemistry video, "Proteins: Structure and Function" (UTS #3615); UTS requires a MINIMUM of 48 hours notice

2) You may wish to show a 24 minute movie, "The Structure of Lysozyme" (UTS #1922); UTS requires a minimum of 48 hours notice

3) Display a telephone cord and point out various features of its configuration to help students understand by analogy the terms primary, secondary, and tertiary structure of proteins

d) Denaturation of Proteins

1) Demonstrate the denaturation of the protein in raw egg white (subject to availability) using heat, HCl(aq), and AgNO₃(aq)

2) Demonstrate the effect of pH on the solubility of a protein by gradually adding acid to a basic solution of casein (subject to availability); the protein is soluble at high and low pH, but insoluble at intermediate pH; repeat the demonstration in reverse by adding base to the solution

Chapter 24 - Enzymes

a) Biological Catalysts

1) Show "Enzymes: Regulators of Body Chemistry", an excellent two-part slide presentation with accompanying audiotape narration; the presentation covers virtually every topic in the chapter in 40 minutes. (I need 48 hours notice for UTS if you want to show this.)

2) To remind students of the function of a catalyst, use Co²⁺(aq) to catalyze the decomposition of KNa-tartrate with H₂O₂; the solution turns pink when Co²⁺ is added, then turns bright green as it begins to react vigorously, then returns to pink as the catalyst is regenerated after the reaction

3) Use fresh blood (from chicken livers, subject to availability) to catalyze the decomposition of H₂O₂ (catalase, the enzyme in blood, is an excellent catalyst)

Chapter 29 - Nucleic Acids

a) The Double Helix of DNA - show a model of DNA

b) The Genetic Code - you may wish to show the 29 minute World of Chemistry video, "The Genetic Code" (UTS #3615-2nd program); UTS requires a minimum of 48 hours notice

Note: This listing was prepared by Mary H. Bailey to accompany the fourth edition of Introduction to General, Organic, and Biological Chemistry by Robert J. Ouellette.