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Learn about alcohols, ethers, aldehydes, ketones, their naming, preparation, and reactions. Understand oxidation, reduction, and dehydration of organic compounds.
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Chapter 11 Outline 11.1Alcohols, Ethers, and Related Compounds 11.2 and 11.3Preparation and Reactions 11.4Aldehydes and Ketones 11.5 Oxidation of Aldehydes 11.6 Reduction of Aldehydes and Ketones 11.7Reactions of Alcohols with Aldehydes and Ketones
11.1: Alcohols, Ethers, and Related Compounds Naming Alcohols • When the IUPAC rules are used to name an alcohol, the main chain (the longest continuous carbon chain carrying the -OH group) is numbered from the end nearer the -OH and named by replacing the “e” ending on the name of the corresponding hydrocarbon by adding “ol;” (i.e. methane to methanol). • When a parent chain contains more than two carbon atoms, the position of the -OH group must be specified with a number. • Any alkyl groups (branches) attached to the main chain are identified by name, position, and number of appearances.
Alcohols Thiols Ethers Sulfides Disulfides
Classification of alcohols: 1, 2, and 3 Alcohols • Primary alcohol (1) - the “C” atom carrying the -OH group is attached to one other “C” atom. • Secondary alcohol (2) - the “C” atom carrying the -OH group is attached to two other “C” atoms. • Tertiary alcohol (3) - the “C” atom carrying the -OH group is attached to three other “C” atoms.
H-binding in alcohols: Compared to hydrocarbons with a similar molecular weight, alcohols have relatively high boiling points.
The boiling points of ethers, thiols, sulfides, and disulfides are much lower than those of alcohols with similar molecular weights, because none of these compounds are able to form hydrogen bonds to like molecules. • Ether molecules are slightly polar as a consequence of the C-O-C linkage, but the dipole-dipole attractions that occur between ether molecules are not strong enough to raise boiling points much above those of similar sized hydrocarbons.
Example: Which of the following molecules can form hydrogen bonds to another molecule of the same type?
Exercise: Predict which molecule has the higher boiling point?
11.2 and 11.3: Preparation of alcohols and their reactions Alcohols can be prepared using a nucleophilic substitution reaction, in which an electron-rich atom or group of atoms, called a nucleophile, replaces a leaving group, an easily replaced atom or group of atoms. Chlorine, bromine, and iodine are common leaving groups used in organic chemistry. (See next slide for reaction to form alcohols)
Exercise: Draw the organic product of each nucleophilic substitution reaction.
11.3: Oxidation of alcohols Oxidation – gaining more “O’s”, losing “H’s” Reduction – gaining more “H’s”, losing “O’s”
Exercise: Draw the product expected from each reaction.
Exercise: In Chapter 15 we will study the citric acid cycle, a series of reactions involved in making compounds that can be used in a separate process to manufacture an energy-rich compound called ATP. A reaction early in the citric acid cycle involves the oxidation of an alcohol. Of the two reactants shown below (each is a reactant somewhere in the cycle), which can be oxidized?
Dehydration rxn of alcohols: Alcohols -----> alkenes (lost of OH and H or H2O ---> get a double bond on the product)
Oxidation of thiols by I2: The oxidation of thiols produces a different type of product than obtained from the oxidation of alcohols. On treatment with the oxidizing agent I2, two thiol molecules combine to form a disulfide. The loss of hydrogen atom by each thiol is evidence that oxidation has taken place.
11.4: Aldehydes and Ketones; Naming Aldehydes and Ketones • When naming aldehydes and ketones according to the IUPAC rules, the carbonyl (C=O) must be part of the main chain, which is numbered from the end nearer this C=O group. • Since the carbonyl carbon atom of an aldehyde is always in position number 1, its position is not specified in the name. • For ketones, however, the position of the carbonyl carbon is given, unless the molecule is small enough that there is no question as to where the C=O is located. • Parent chains are named by dropping the final “e” from the name of the corresponding hydrocarbon and adding “al” for aldehydes or “one” for ketones.
General physical properties of aldehydes and ketones: • Aldehydes and ketones have much lower boiling points than alcohols with a similar molecular weight. • The differences in boiling points is due to the fact that alcohols can form hydrogen bonds while aldehydes and ketones cannot. • The C=O is slightly polar, which allows an aldehyde or ketone to interact with one another through dipole-dipole forces. The polarity of the carbonyl group and its ability to form hydrogen bonds with water molecules allows small aldehydes and ketones to be highly water soluble (“like dissolves like”).
11.6: Reduction of Aldehydes and Ketones Reactant Product (more O’s, less H’s) (more H’s, less O’s; gaining more H’s)
Examples: Draw the alcohol product expected from each reduction reaction.
Exercises: What is the organic reactant that would undergo the reaction below to give the product shown in each reaction?
11.7: Reactions of Alcohols with Aldehydes and Ketones (Hemiacetal and Hemiketals) When an aldehyde or ketone is reacted with one alcohol molecule a hemiacetalis formed. (Hemiacetals formed from ketones are also known as hemiketals). A hemiacetal consists of a carbon atom that is attached to both -OH and -OC.
These are hemiacetals and hemiketals! How do I recognize them?
(Acetals and ketals) When two alcohol molecules react with an aldehyde or ketone in the presence of H+, an acetal forms. An acetal consists of a carbon atom that is attached to two -OC groups. (Acetals formed from ketones are also known as ketals).
Exercises: Draw the organic product of each reaction.
Exercises: (More Practice make you better!) Draw the missing reactant for each reaction.
Drugs in the Environment What functional groups are present on these drug molecules?
