Announcements & Agenda (03/12/07)

Announcements& Agenda(03/12/07) • Pick Up Quizzes • Exam THIS Wednesday! • Covers Ch 7, 8, 10-12 (not 12.6, on Exam 3) • Practice Exam & Key Posted! • Review TONIGHT @ 6:30p (Room 1019) • Today • Ethers & Thiols • Aldehydes & Ketones (12.4-12.5) • Note Benedict’s Test, Tollen’s Test, & Iodoform Test will not be on Wednesday’s Exam!

Last Time: Alcohol Classification • determined by the number of alkyl groups directlyattached to the carbon bonded to the hydroxyl. • primary (1°), secondary (2°), or tertiary(3). Primary (1º) Secondary (2º) Tertiary (3º)1 group 2 groups 3 groupsHCH3CH3| | | CH3—C—OH CH3—C—OH CH3—C—OH| | | H H CH3

Last Time: Dehydration of Alcohols • Alcohols dehydratewhen heated with an acid catalyst • Lose —H and —OH from adjacent carbon atoms HOH | | H—C—C—H H+, heat H—C=C—H + H2O | | | | H H H H alcohol alkene

This is a carbonyl group… Last Time: Oxidation of 1Alcohols When a primary alcohol is oxidized, [O], • one H is removed from the –OH. • another H is removed from the C bonded to -OH. • an aldehyde is produced. [O] PrimaryalcoholAldehyde OH O | [O] || CH3—C—H CH3—C—H + H2O | H Ethanol Ethanal (ethyl alcohol) (acetaldehyde) NOTE: If enough oxidant around, will go on to form carboxylic acid!

Oxidation of Secondary (2) Alcohols When a secondary alcohol is oxidized, [O], • one H is removed from the –OH. • another H is removed from the C bonded to -OH. • a ketone is produced. [O] secondary alcoholketone OH O │ [O] ║ CH3─C─CH3 CH3─C─CH3 + H2O │ H 2-propanol (isopropyl alcohol) 2-propanol (dimethyl ketone)

Oxidation of Tertiary ( 3)Alcohols Tertiary 3 alcohols do not readily oxidize. [O] Tertiary alcohol no reaction OH │ [O] CH3─C─CH3 no product │ CH3 no H on the C-OH to oxidize 2-methyl-2-propanol

Oxidation of Ethanol in the Body In the body, • enzymes in the liver oxidize ethanol. • aldehyde product impairs coordination. • blood alcohol over 0.4% can be fatal. O O ║ ║ CH3CH2OH CH3CH CH3COH 2CO2 + H2O ethanol acetaldehyde acetic acid

Ethanol CH3CH2OH • acts as a depressant. • kills or disables more people than any other drug. • is metabolized at a rate of 12-15 mg/dL per hour by a social drinker. • is metabolized at a rate of 30 mg/dL per hour by an alcoholic.

Effect of Alcohol on the Body

Alcohol Contents in Common Products % Ethanol Product 50% Whiskey, rum, brandy 40% Flavoring extracts 15-25% Listerine, Nyquil, Scope 12% Wine, Dristan, Cepacol 3-9% Beer, Lavoris

Ethers • contains an ─O─ between two carbon groups (R-O-R’). • has a common name that gives the alkyl names of the attached groups followed by ether. CH3─O─CH3 CH3─CH2─O─CH3 dimethyl ether ethyl methyl ether

Boiling Points of Ethers Ethers • are only modestly polar. • have an O atom, but there is no H attached. • cannot form hydrogen bonds between ether molecules.

Solubility of Alcohols & Ethers in Water Alcohols and ethers • are more soluble in water than alkanes because the oxygen atom can hydrogen bond with water. • with 1-4 C atoms are soluble, but not with 5 or more C atoms.

Comparing Solubility & Boiling Points Molar Boiling Soluble Compound Mass Point (°C) in Water? Alkane CH3─CH2─CH3 44 -42 No Ether CH3─O─CH3 46 -23 Yes Alcohol CH3─CH2─OH46 78 Yes

Ethers as Anesthetics Anesthetics • inhibit pain signals to the brain. • like diethyl ether CH3─CH2─O─CH2─CH3 were used for over a century, but caused nausea and were flammable. • developed by the 1960’s were nonflammable. Cl F F Cl F H │ │ ││ │ │ H─C─C─O─C─H H─C─C─O─C─H │ │ ││ │ │ F F F H F H Ethane(enflurane) Penthrane

MTBE Methyl tert-butyl ether CH3 │ CH3─O─C─CH3 │ CH3 • is second in production of organic chemicals. • is an additive used to improve gasoline performance. • use is questioned since the discovery that MTBE has contaminated water supplies.

Thiols • are carbon compounds that contain a –SH group. • are named in the IUPAC system by adding thiolto the alkane name of the longest carbon chain. • the -SH group may also be called a “mercapto” group

Thiols Thiols • often have strong odors. • are used to detect gas leaks. • are found in onions, oysters, and garlic.

Oxidation of Thiols When thiols undergo oxidation, • an H atom is lost from each of two –SH groups. • the product is a disulfide. [O] CH3─SH + HS─CH3 CH3─S─S─CH3 + H2O

Aldehydes and Ketones An aldehyde contains a carbonyl group (C=O), which is a carbon atom with a double bond to an oxygen atom. In a ketone, the carbon of the carbonyl group is attached to two other carbon atoms.

Naming Aldehydes

Aldehydes in Flavorings Several naturally occurring aldehydes are used as flavorings for foods and fragrances. Benzaldehyde (almonds) Cinnamaldehyde (cinnamon)

Naming Ketones • as IUPAC, the -e in the alkane name is replaced with –one. • With a common name, the alkyl groups attached to the carbonyl group are named alphabetically followed by ketone. OO ║ ║ CH3 ─C─CH3 CH3─C─CH2─CH3propanone 2-butanone (dimethyl ketone) (ethyl methyl ketone)

Ketones in Common Use Nail polish remover, solvent Propanone, Dimethylketone, Acetone Butter flavoring

Properties of Aldehydes & Ketones • The polar carbonyl group provides dipole-dipole interactions. + -+ - C=O C=O • Without an H on the oxygen, aldehydes and ketones cannot form hydrogen bonds to each other.

Boiling Points Aldehydes and ketones have • polar carbonyl groups (C=O). + - C=O • attractions between polar groups. + -+ - C=O C=O • higher bp’s than alkanes and ethers of similar mass. • lower bp’s than alcohols of similar mass.

Comparison of Boiling Points

Solubility in Water The electronegative O atom of the carbonyl group of aldehydes and ketones forms hydrogen bonds with water.

Tollens’ Test • Tollens’ reagent, which contains Ag+, oxidizes aldehydes, but not ketones. • Ag+ is reduced to metallic Ag, which appears as a “mirror” in the test tube.

Benedict’s Test • Benedict’s reagent, which contains Cu2+,reacts with aldehydes that have an adjacent OH group. • An aldehyde is oxidized to a carboxylic acid, while Cu2+ is reduced to give red Cu2O(s).

Announcements & Agenda (03/12/07)