13 Hydrocarbon Derivatives II

Name: 13 Hydrocarbon Derivatives II
Uploaded: 2017-10-01T14:03:19+00:00
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Description: 13 Hydrocarbon Derivatives II

13 Hydrocarbon Derivatives II
Compounds with carbon-oxygen double bonds Aldehydes Ketones Carboxylic Acids Esters Amides Copyright © Houghton Mifflin Company. All rights reserved.

13.2 Naming Aldehydes Suffix is “-al”
Find longest chain that bears carbonyl Number carbon chain so carbonyl is #1 Locate and name any other substituents Final “e” on name of hydrocarbon is dropped Copyright © Houghton Mifflin Company. All rights reserved.

13.2 Naming Aldehydes Common names are frequently used too.
Copyright © Houghton Mifflin Company. All rights reserved.

13.2 Naming Aldehydes Aromatic aldehydes are named as benzaldehydes.

13.4 Naming Ketones Suffix is “-one”
Find longest chain that bears carbonyl Number carbon chain so carbon bearing C=O has lowest possible number; it cannot be #1 Locate and name any other substituents Final “e” on name of hydrocarbon is dropped Copyright © Houghton Mifflin Company. All rights reserved.

13.4 Naming Ketones Common names are frequently used. They are formed by naming the alkyl substituents on the carbonyl, usually in alphabetical order. Copyright © Houghton Mifflin Company. All rights reserved.

13.4 Naming Ketones Compounds with carbonyl groups in rings are named as cycloalkanones. The carbonyl carbon is #1; this locant is understood and not given. Copyright © Houghton Mifflin Company. All rights reserved.

13.4 Naming Ketones Acetyl groups are carbonyl groups bonded to methyl groups. “Acet-” and “aceto-” appear often in names of carbonyl compounds. Copyright © Houghton Mifflin Company. All rights reserved.

13.3,5 Properties of Aldehydes and Ketones
Aldehydes and ketones have similar prop-erties and undergo similar reactions. These will be considered together. Aldehydes and ketones are polar, but are not hydrogen bond donors. Their boiling points are intermediate between alcohols and alkanes/ethers. Copyright © Houghton Mifflin Company. All rights reserved.

13.3,5 Properties of Aldehydes and Ketones
Aldehydes and ketones have similar prop-erties and undergo similar reactions. These will be considered together. Copyright © Houghton Mifflin Company. All rights reserved.

13.3,5 Properties Aldehydes and ketones can act as hydrogen bond acceptors. Small compounds are appreciably soluble in water. Formaldehyde, acetaldehyde, and acetone are completely soluble in water. Copyright © Houghton Mifflin Company. All rights reserved.

13.3,5 Reactions Aldehydes are generally more reactive than ketones, and can undergo some reactions that ketones do not. There are more sim-ilarities than differences. Copyright © Houghton Mifflin Company. All rights reserved.

Ketones are not easily oxidized.
13.3,5 Reactions Aldehydes are easily oxidized to carboxylic acids. Ketones are not easily oxidized. Copyright © Houghton Mifflin Company. All rights reserved.

13.3,5 Reactions Aldehydes and ketones can be reduced to alcohols.

13.3,5 Reactions Catalytic hydrogenation works, but more often NaBH4 or LiAlH4 is used. These compounds behave as sources of hydride anion, H1–. Copyright © Houghton Mifflin Company. All rights reserved.

13.3,5 Reactions Hydration is addition of water across the C=O bond. It is similar to addition across a C=C bond. Aldehydes hydrate more readily than ketones. Formaldehyde hydrates completely. Formalin is a solution of hydrated formaldehyde. Copyright © Houghton Mifflin Company. All rights reserved.

13.3,5 Reactions Alcohols can add across a C=O bond. The product is called a hemiacetal. Ketones undergo the same reaction, but less readily. The product is sometimes called a hemiketal. We’ll call both types hemiacetals. Copyright © Houghton Mifflin Company. All rights reserved.

13.3,5 Reactions Hemiacetals have ether and hydroxyl groups on the same carbon. The two structures are in equilibrium, and the hemiacetal can be difficult to isolate. Copyright © Houghton Mifflin Company. All rights reserved.

13.3,5 Reactions In the presence of excess alcohol, acetals form. Acetals of ketones may be called ketals. The equilibrium is not favorable for the reac-tion. Catalysis speeds it up, and water removal drive it to completion. Copyright © Houghton Mifflin Company. All rights reserved.

13.3,5 Reactions Diols give cyclic acetals.

Common Aldehydes Formaldehyde, the simplest aldehyde, is used for sterilizing apparatus and as an embalm-ing fluid. It is also a component of synthetic resins, e.g. phenol-formaldehyde (Bakelite), and melamine-formaldehyde (Formica). Copyright © Houghton Mifflin Company. All rights reserved.

Common Aldehydes Aldehydes are components of flavors and odors.

Common Ketones Simple ketones are solvents and degreasers.
Simple aldehydes are too reactive and toxic to be used as solvents. Copyright © Houghton Mifflin Company. All rights reserved.

Common Ketones Ketones are functional groups in some steroid hormones.

13.6 Carboxylic Acids Carboxylic acids have a carboxyl group (COOH) on a hydrocarbon chain; R–COOH The carboxyl group has a hydroxyl group on a carbonyl carbon. Copyright © Houghton Mifflin Company. All rights reserved.

13.6 Naming Carboxylic Acids
Suffix is “-oic acid” Find longest chain that bears –COOH Number carbon chain so –COOH is #1 Locate and name any other substituents Final “e” on name of hydrocarbon is dropped Copyright © Houghton Mifflin Company. All rights reserved.

13.7 Properties of Carboxylic Acids
Carboxylic acids with up to nine carbon atoms are liquids with pungent odors. Acetic acid, in vinegar, is a good example. “Acet” comes from “vinum acetum,” sour wine. Larger molecules are waxy solids, as are aromatic carboxylic acids. Copyright © Houghton Mifflin Company. All rights reserved.

13.7 Properties Carboxylic Acids

13.7 Acidity of Carboxylic Acids
Carboxylic acids are proton donors. When R is alkyl, Keq is about 10–5. Keq = [H3O1+][RCOO1–] [RCOOH][H2O] Less than 5% of the molecules are ionized. Copyright © Houghton Mifflin Company. All rights reserved.

13.7 Naming Carboxylate Salts
Carboxylate anions are named as the “-ate” anion of the conjugate acid. Copyright © Houghton Mifflin Company. All rights reserved.

13.7 Naming Carboxylate Salts
Ionic compounds are also called “salts.” Those that contain carboxylate anions are named with the cation (usually a metal) followed by the name of the carboxylate. Copyright © Houghton Mifflin Company. All rights reserved.

13.7 Reactions of Carboxylic Acids
Acid-base reactions: Carboxylic acids equilibrate with their conjugate bases in water. RCOOH + H2O  RCOO1– + H3O1+ Carboxylic acids deprotonate to carboxylate salts in strong bases. RCOOH + OH1–  RCOO1– + H2O Carboxylate anions are protonated in strong acids. RCOO1– + H3O1+  RCOOH + H2O Copyright © Houghton Mifflin Company. All rights reserved.

Condensation reactions: Condensation reactions are reactions in which two molecules combine into one, with the expulsion of a small molecule such as water. The dehydration of alcohols to form ethers is a condensation reaction. Copyright © Houghton Mifflin Company. All rights reserved.

Esters are produced by the condensation of a carboxylic acid and an alcohol. Keq is often near 1. In the classic Fischer Esterification, H2SO4 is the catalyst. Copyright © Houghton Mifflin Company. All rights reserved.

Amides are produced by the condensation of a carboxylic acid and ammonia or an amine. The amine must have at least one hydrogen, or water cannot form. Copyright © Houghton Mifflin Company. All rights reserved.

Direct formation of amides from carboxylic acids and amines is complicated by the acid-base reaction between reactants. “Heat” means > 200C (>400F) to decompose the salt and form the amide. Copyright © Houghton Mifflin Company. All rights reserved.

Important Carboxylic Acids
Direct formation of amides from carboxylic acids and amines is complicated by the acid-base reaction between reactants. “Heat” means > 200C (>400F) to decompose the salt and form the amide. Copyright © Houghton Mifflin Company. All rights reserved.

13.8 Esters Esters are derivatives of carboxylic acids.
They have an alkoxy group (–OR) on a carbonyl carbon. Copyright © Houghton Mifflin Company. All rights reserved.

13.8 Naming Esters Esters are condensation products of alcohols and carboxylic acids. They are named as alkyl alkanoates. The alkyl group is de-rived from the alcohol; the alkanoate is de-rived from the acid. The -oic acid suffix or the acid is replaced by -ate. Copyright © Houghton Mifflin Company. All rights reserved.

13.9 Properties of Esters Esters are polar, but cannot form hydrogen bonds. They are slightly soluble in water. Boiling points are somewhat lower than those of structurally similar ketones. Copyright © Houghton Mifflin Company. All rights reserved.

13.9 Reactions of Esters Hydrolysis:
The main reaction of esters is hydrolysis (breaking with water). It is the reverse of the condensation reaction. Like formation of the ester, Keq is ~1. Excess water increases the amount of hydrolyzed product. Copyright © Houghton Mifflin Company. All rights reserved.

13.9 Reactions of Esters Hydrolysis of esters in base is called saponification, a.k.a. soap-making! One uses at least an equivalent of OH1–, and the acid is isolated as its carbox-ylate salt. Formation of the salt drives the reaction to completion. Copyright © Houghton Mifflin Company. All rights reserved.

13.9 Reactions of Esters Transesterification:
It is often easier to prepare complex esters or amides from simple esters than from the acids. Copyright © Houghton Mifflin Company. All rights reserved.

13.10 Naming Amides Suffix is “amide”
1. Root is derived from carboxylic acid 2. IUPAC names for secondary and tertiary amides involve use of the prefix “N-” for the amine substituents. If the same group appears twice, use “di-” and prefix. 3. IUPAC names for amides of simple acids allow the acid’s common name to be used. Copyright © Houghton Mifflin Company. All rights reserved.

13.10 Naming Amides Compounds in which carbonyl groups appear on either side of the nitrogen are called imides. Cyclic imides are more common than straight-chain molecules. Copyright © Houghton Mifflin Company. All rights reserved.

13.11 Properties of Amides Amides have resonance structures that cause the nitrogen atom to be trigonal planar, sp2. Rotation about the CN bond is restricted. Copyright © Houghton Mifflin Company. All rights reserved.

13.11 Properties of Amides 1 and 2 amides have strong dipoles and hydrogen bonds. For 2 amides, the fa-vored conformation has the H atom op-posite the O atom. The dipole-dipole forces and hydro-gen bonds are quite strong. Copyright © Houghton Mifflin Company. All rights reserved.

13.11 Properties of Amides 1 and 2 amides have the highest melting and boiling points of common compounds. 3 amides are usually high-boiling liquids. Copyright © Houghton Mifflin Company. All rights reserved.

Important Amides Simple amides: various small molecules

Important Amides Barbiturates:
Barbituric acid is the parent compound for many central nervous system depressants. They are used as sedatives and anesthetics. Copyright © Houghton Mifflin Company. All rights reserved.

13.12 Condensation Polymers
Condensation reactions between polyfunctional carboxylic acids and alcohols or amines produce a wide variety of polymers. They are called condensation polymers or step-growth polymers because of how they form. Polymers formed from alkenes are called chain-growth polymers or addition polymers. Copyright © Houghton Mifflin Company. All rights reserved.

Important Polyesters Polyesters are formed in reactions between diacids and diols. Polyamides are formed in reactions between diacids and diamines. Copyright © Houghton Mifflin Company. All rights reserved.

In the “nylon rope trick” polymer forms at the interface of a water solution of hexane di-amine and an organic solution of adipoyl chloride (adipic acid on steroids!). Copyright © Houghton Mifflin Company. All rights reserved.

Nylon 6 was developed in Germany. It is made by ring-opening, rather than condensation. Nylons are very strong fibers because of inter-chain hydrogen bonding. There are regions of microcrystallinity, highly or-dered chain segments, in the material. Copyright © Houghton Mifflin Company. All rights reserved.

Aramids are polyamides with aromatic com-ponents. They are even stronger than Nylon 6,6, and are used for demanding applications, such as armor. Copyright © Houghton Mifflin Company. All rights reserved.

Polyurethanes are polymeric carbamates. They are resilient, elastomeric, and can be made into foams. There are many structures, but most involve reactions between diisocyan-ates and diols. Copyright © Houghton Mifflin Company. All rights reserved.

Proteins and peptides are naturally-occurring polyamides formed from amino acids. There are ~20 amino acids with different R’s. Proteins are long polymers, n > Peptides are short polymers, n < 50 Copyright © Houghton Mifflin Company. All rights reserved.

13 Hydrocarbon Derivatives II

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