Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 12 Lecture Outline Prepared by Jennifer N. Robertson-Honecker West Virginia University

Organic Compounds that Contain Oxygen or Sulfur Three families of compounds that contain a C atom singly bonded to O or S are: 1.Alcohols, which contain an OH (hydroxyl) group 2.Ethers, which have two alkyl groups bonded to an O atom 2

Organic Compounds that Contain Oxygen or Sulfur Two families of compounds that contain a carbonyl group C=O: 1.Aldehydes, which have at least one H atom bonded to the carbonyl carbon 2.Ketones, which have two alkyl groups bonded to the carbonyl carbon 3

Structure and Properties of Alcohols Alcohols contain a hydroxyl (OH) group. Alcohols are classified by the number of C atoms bonded to the C with the OH group. A primary (1 o ) alcohol has an OH group on a C bonded only to 1 C atom. 1o1o 4

Structure and Properties of Alcohols A secondary (2 o ) alcohol has an OH group on a C bonded only to 2 C atoms. 2o2o 3o3o A tertiary (3 o ) alcohol has an OH group on a C bonded only to 3 C atoms. 5

Structure and Properties of Alcohols An alcohol (ROH) contains an O atom with a bent shape like H 2 O and a bond angle similar to a tetrahedral. 6 Alcohols have an H atom bonded to an O atom, making them capable of intermolecular hydrogen bonding. This gives alcohols much stronger intermolecular forces than hydrocarbons.

Structure and Properties of Alcohols As a result, alcohols have higher boiling and melting points than hydrocarbons of comparable size and shape. stronger intermolecular forces higher boiling and melting point 7 melting point: -138 ºC boiling point: -0.5 ºC melting point: -127 ºC boiling point: 97 ºC

Structure and Properties of Alcohols Alcohols are soluble in organic solvents. Low molecular weight alcohols (6 C’s or less) are soluble in water. Higher molecular weight alcohols (6 C’s or more) are not soluble in water. 2 C’s in chain water soluble 8 C’s in chain water insoluble 8

Nomenclature of Alcohols Find the longest carbon chain containing the carbon bonded to the OH group. Number the carbon chain to give the OH group the lower number, and apply all other rules of nomenclature. 9 In the IUPAC system, alcohols are identified by the suffix -ol. To name an alcohol:

Nomenclature of Alcohols Give the IUPAC name of the following alcohol. Step [1] Find the longest carbon chain containing the C bonded to the OH group. 5 C’s in longest chain pentane ----> pentanol Change the –e ending of the parent alkane to the suffix –ol. 10 Sample Problem 12.2

Nomenclature of Alcohols Step [2] Number the carbon chain to give the OH group the lower number, and apply all other rules of nomenclature. 1-pentanol Answer 3,3-dimethyl-1-pentanol 11

Nomenclature of Alcohols When an OH group is bonded to a ring, the OH is automatically on C1. The “1” is usually omitted from the name. The ring is then numbered to give the next substituent the lower number. 12

Structure and Properties of Ethers Ethers (ROR) have two alkyl groups bonded to an O atom. 13 The O atom of an ether has a bent shape like H 2 O and a bond angle similar to a tetrahedral.

Structure and Properties of Ethers Physical Properties Ether has two polar C—O bonds with a bent shape, therefore it has a net dipole. Ether does not contain an H atom bonded to an O atom, so ether cannot form intermolecular hydrogen bonds. 14

Structure and Properties of Ethers Physical Properties These facts give ethers: As a result, ethers of comparable size and shape tend to have: stronger intermolecular forces than alkanes weaker intermolecular forces than alcohols higher melting and boiling points than hydro- carbons lower melting and boiling points than alcohols 15

Structure and Properties of Ethers Physical Properties 16

Structure and Properties of Ethers Physical Properties Ethers are soluble in organic solvents. Low molecular weight ethers (5 C’s or less) are soluble in water, as water can hydrogen bond to the ether’s O atom. Higher molecular weight ethers (6 C’s or more) are not soluble in water. 17

Focus on Health & Medicine Ethers as Anesthetics A general anesthetic is a drug that interferes with nerve transmission in the brain, resulting in a loss of consciousness and the sensation of pain. Modern variations include the three ethers below: 18 Diethyl ether was first demonstrated as an anesthetic in the nineteenth century.

Reactions of Alcohols Dehydration Dehydration is the loss of H 2 O from a starting material. It occurs when an alcohol is treated with a strong acid like H 2 SO 4, and forms an alkene product. Dehydration is an example of an elimination reaction, in which parts of the starting material are “lost” and a multiple bond is formed. 19

Reactions of Alcohols Dehydration Examples: 20

Reactions of Alcohols Oxidation Oxidation results in an: increase in the number of C—O bonds decrease in the number of C—H bonds The symbol [O] indicates an oxidation reaction. 21

Reactions of Alcohols Oxidation Oxidation occurs by replacing the C—H bonds on the carbon bearing the OH group by C—O bonds. All oxidation products from alcohol starting materials contain a C=O, a carbonyl group. 22

Reactions of Alcohols Oxidation Primary (1 o ) alcohols first oxidize to aldehydes (RCHO), replacing 1 C—H with 1 C—O. Aldehydes are further oxidized to carboxylic acids (RCOOH), replacing 1 C—H with 1 C—O. 1 o alcohol (ROH) aldehyde (RCHO) carboxylic acid (RCOOH) 23

Reactions of Alcohols Oxidation Secondary (2 o ) alcohols are oxidized to ketones (R 2 CO) replacing 1 C—H with 1 C—O. 24

Reactions of Alcohols Oxidation Tertiary (3 o ) alcohols have no H atoms on the C with the OH group, so they are not oxidized. 25

The oxidation of ethanol with K 2 Cr 2 O 7 was the first available method for the routine testing of alcohol concentration in exhaled air. Focus on The Human Body Oxidation and Blood Alcohol Screening 26 Oxidation with K 2 Cr 2 O 7 is characterized by a color change, as the red-orange reagent is reduced to a green Cr 3+ product.

Focus on Health & Medicine The Metabolism of Ethanol When ethanol is consumed it is quickly absorbed in the stomach and small intestines. In the liver, the enzymes alcohol and aldehyde dehydrogenase act as oxidizing reagents. CH 3 CH—OH ethanol [O] CH 3 H C O acetaldehyde [O] CH 3 OH C O acetic acid Consuming more ethanol than can be metabolized leads to a buildup of acetaldehyde, which is toxic. 27

Organic Compounds that Contain Sulfur To make straight hair curly, the disulfide bonds holding the hair proteins together are reduced. The hair is then turned around curlers, and an oxidizing agent is applied. This re-forms the disulfide bonds in the hair, now giving it a curly appearance. 28

Aldehydes and Ketones Structure and Properties of Aldehydes and Ketones Two families of compounds contain a carbonyl group: 29 Aldehydes (RCHO) Ketones (RCOR or R 2 CO)

The carbonyl carbon atom is trigonal planar, with bond angles of 120 o. O is more electronegative than C, so the carbonyl group is polar. The carbonyl C is e − rich (δ − ) and the carbonyl O is e − poor (δ + ). 30 Aldehydes and Ketones Structure and Properties of Aldehydes and Ketones

Nomenclature Naming Aldehydes To name an aldehyde using the IUPAC system: Find the longest chain containing the CHO group. Change the “-e” ending of the parent alkane to “-al”. Number the chain to put the CHO group at C1, but omit “1” from the name. Apply all other nomenclature rules. CH 3 CHCH CH 3 C O H butane  butanal 123 Answer: 2,3-dimethylbutanal 31

Nomenclature Naming Aldehydes Common names are used for simple aldehydes; the names contain the suffix “-aldehyde”. formaldehydeacetaldehydebenzaldehyde 32

Nomenclature Naming Ketones To name a ketone using the IUPAC system: Find the longest chain containing the carbonyl group. Number the chain to give the carbonyl carbon the lower number. Apply all other nomenclature rules. CHCH 2 CH 3 CH 3 C O pentane  pentanone Change the “-e” ending of the parent alkane to “-one”. 23 Answer: 3-methl-2-pentanone 1 33

Nomenclature Naming Ketones With cyclic ketones, numbering begins at the carbonyl carbon, “1” is omitted from the name. 34 The ring is then numbered clockwise or counterclockwise to give the first substituent the lower number. Name the ring. cyclohexane  cyclohexanone Sample Problem 12.7 Step [1]

Nomenclature Naming Ketones 35 Number and name the substituents, making the C=O C1. Sample Problem 12.7 Step [2] Answer: 3-ethyl-4-methylcyclohexanone

Nomenclature Naming Ketones Three simple ketones have widely used common names: acetoneacetophenonebenzophenone 36

Physical Properties Aldehydes and ketones have higher boiling points than similar hydrocarbons because: they are polar molecules they have stronger intermolecular forces than alkanes and alkenes Increasing boiling point CH 3 CH 2 CH 2 CH 2 CH 3 pentane bp 36 o C CH 3 CH 2 CH 2 CHO butanal bp 76 o C 37

Physical Properties Aldehydes and ketones have lower boiling points than similar alcohols because: They do not have an O—H bond. Therefore, they cannot have intermolecular hydrogen bonding. Thus, they have weaker intermolecular forces than alcohols. Increasing boiling point CH 3 CH 2 COCH 3 2-butanone bp 80 o C CH 3 CH 2 CH 2 CH 2 OH 1-butanol bp 118 o C 38

Physical Properties Aldehydes and ketones are soluble in organic solvents. Those molecules with less than 6 C’s are soluble in both organic solvents and water. Those molecules with 6 C’s or more are soluble in organic solvents, but insoluble in water. 39

Focus on Health & Medicine Interesting Aldehydes and Ketones Cinnamaldehyde, the major component of cinnamon bark: Vanillin, the primary component of the extract of the vanilla bean: 40

Focus on Health & Medicine Interesting Aldehydes and Ketones Geranial, the characteristic odor of lemon grass, used in perfumery and in synthesis of vitamin A: Citronellal, the odor of citronella candles, used to repel mosquitoes: 41

Focus on Health & Medicine Interesting Aldehydes and Ketones Acetone [(CH 3 ) 2 C=O] is the simplest ketone: It is produced in the breakdown of fatty acids in the body. Unusually high levels are found in diabetic patients. 42 Dihydroxyacetone, the active ingredient in sunless tanning agents, reacts with proteins in the skin to produce a colored pigment:

Oxidation of Aldehydes 43 Aldehydes contain a hydrogen atom bonded directly to the carbonyl carbon; they can be oxidized to carboxylic acids:

Reactions of Aldehydes and Ketones Oxidation of Aldehydes In oxidation, the aldehyde C—H bond is converted into a carboxylic acid C—OH bond. 44

Reactions of Aldehydes and Ketones Oxidation of Aldehydes Ketones cannot be oxidized because there is no C—H bond. 45

Reactions of Aldehydes and Ketones Oxidation of Aldehydes Aldehydes can be selectively oxidized in the presence of other functional groups using the Tollens reagent. 46

47 Stereochemistry is the 3-dimensional structure of compounds. The cis and trans examples below are stereoisomers Looking Glass Chemistry Molecules and Their Mirror Images Stereoisomers differ only in the 3-dimensional arrangement of atoms.

48 Molecules and Their Mirror Images What It Means to be Chiral or Achiral Left hands and right hands are mirror images of each other.

49 Molecules and Their Mirror Images What It Means to be Chiral or Achiral Left and right hands are not identical (nonsuperimposable). A molecule that is not superimposable on its mirror image is chiral.

50 Molecules and Their Mirror Images What It Means to be Chiral or Achiral Two socks from a pair are mirror images that are superimposable. A molecule that is superimposable on its mirror image is achiral.

51 Molecules and Their Mirror Images The Chirality of Molecules To determine whether a molecule is chiral or achiral we must examine what groups are bonded to each carbon atom: A chiral molecule has at least one carbon atoms bonded to four different groups. To superimpose a molecule and its mirror image you can perform any rotation but you cannot break bonds. An achiral molecule does not contain a carbon atom bonded to four different groups.

52 Molecules and Their Mirror Images The Chirality of Molecules For CH 2 BrCl: Rotate the molecule to align bonds:

53 Molecules and Their Mirror Images The Chirality of Molecules For CHBrClF:

54 Molecules and Their Mirror Images The Chirality of Molecules The two mirror images of CHBrClF are enantiomers, mirror images that are not superimposable. A carbon atom with four different groups like CHBrClF is called a chirality center. A molecule that is not superimposable on its mirror image is a chiral molecule.

55 Chirality Centers Locating Chirality Centers To locate a chirality center, look at each tetrahedral C atom in a molecule. Look at the four groups—not the four atoms— bonded to it.

56 Chirality Centers Locating Chirality Centers We consider all atoms in a group as a whole unit.

57 Chirality Centers Locating Chirality Centers A C atom bonded to two or more like groups is never a chirality center. CH 2 and CH 3 groups have more than one H atom bonded to the same C, so those C’s are never chirality centers. A C that is part of a multiple bond does not have four groups around it, so it is never a chirality center.

58 Chirality Centers Locating Chirality Centers Chirality centers in the examples below are labeled in red:

59 Fischer Projections A Fischer Projection takes a 3-D tetrahedral shape, and re-draws it. A carbon atom is located at the intersection. The horizontal bonds come forward, on the wedges. The vertical bonds go back, on the dashed lines.

60 Fischer Projections We can draw the cross and Fischer projection for both enantiomers of 2-butanol:

61 Focus on Health & Medicine Chiral Drugs Many drugs are chiral, and often they must interact with a chiral receptor to be effective. One enantiomer of a drug may be effective in treating a disease whereas its mirror image may be ineffective. One enantiomer may “fit” the chiral receptor and evoke a specific response. Its mirror image may not fit the same receptor, making it ineffective.

62 Focus on Health & Medicine Chiral Drugs

63 Focus on Health & Medicine Chiral Pain Relievers Ibuprofen is an active anti-inflammatory agent whose enantiomer is inactive, and is sold as a racemic mixture.

64 Focus on Health & Medicine Parkinson’s Disease and L-Dopa L-Dopa, a dopamine precursor, is used to help treat the dopamine deficient brains of Parkinson’s patients. Dopamine cannot be directly taken by a patient because it cannot cross the blood-brain barrier.