23.3 carbonyl compounds > 1 copyright © pearson education, inc., or its affiliates. all rights...

Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

23.3 Carbonyl Compounds >23.3 Carbonyl Compounds >

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Chapter 23Functional Groups

23.1 Introduction to Functional Groups

23.2 Alcohols, Ethers, and Amines

23.3 Carbonyl Compounds

23.4 Polymers



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What gives a banana its characteristic smell?

CHEMISTRY & YOUCHEMISTRY & YOU

Many organic molecules have pleasant aromas.



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Aldehydes and Ketones

What structural characteristic do an aldehyde and a ketone share?

Aldehydes and KetonesAldehydes and Ketones



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An oxygen atom can also be bonded to a single carbon atom by a double covalent bond.

• A carbonyl group is a functional group with the general structure C O.



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The C O functional group is present in aldehydes and ketones.



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• The general formula of an aldehyde is RCHO.


An aldehyde is an organic compound in which the carbon of the carbonyl group is joined to at least one hydrogen.



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• The general formula of a ketone is RCOR.


A ketone is an organic compound in which the carbon of the carbonyl group is joined to two other carbons.



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The IUPAC system may be used for naming aldehydes and ketones.

• First identify the longest carbon chain that contains the carbonyl group.

• Replace the -e ending of the parent structure with -al to designate an aldehyde.

– In the IUPAC system, the continuous chain aldehydes are named methanal, ethanal, propanal, butanal, and so forth.




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The IUPAC system may be used for naming aldehydes and ketones.

• Ketones are named by changing the ending of the longest continuous carbon that contains the carbonyl group from -e to -one.

– If the carbonyl group of a ketone could occur at more than one place on the chain, then its position is designated by the lowest possible number.




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Some Common Aldehydes

IUPAC name (common name)

Structural formula Ball-and-stick model

Methanal(formaldehyde)

Ethanal(acetaldehyde)

Benzaldehyde(benzaldehyde)

Interpret DataInterpret Data



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Some Common Ketones

IUPAC name (common name)

Structural formula Ball-and-stick model

Propanone(acetone)

Diphenylmethanone(benzophenone)




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The simplest aldehyde is methanal (HCHO), also called formaldehyde.

• Its greatest use is in the manufacture of synthetic resins.

• A 40% aqueous solution of methanal, known as formalin, can be used to preserve biological specimens.


Uses of Aldehydes and Ketones



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The most common industrial ketone is propanone, also called acetone.

• Propanone is used in industry as a solvent for resins, plastics, and varnishes.

• Many nail-polish removers contain propanone as well.





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• Benzaldehyde is also known as oil of bitter almond because it is largely responsible for the taste and aroma of almonds.

• Many flavoring agents, including vanilla bean extract and cinnamon sticks, contain aromatic aldehydes.



A wide variety of aldehydes and ketones have been isolated from plants and animals. Many have fragrant odors.



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• Aldehydes and ketones cannot form intermolecular hydrogen bonds because they lack —OH and —NH groups.

– They have boiling points that are lower than those of corresponding alcohols.

• Aldehydes and ketones can attract each other, however, through polar-polar interactions of their carbonyl groups.

– Their boiling points are higher than those of the corresponding alkanes.


Properties of Aldehydes and Ketones



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Some Organic Compounds with Three Carbons

Compound FormulaBoiling Point

(°C)

Primary intermolecular

interactions

Propane CH3CH2CH3 –42Dispersion

forces

Propanal CH3CH2CHO 49Polar-polar interactions

Propanone CH3COCH3 56Polar-polar interactions

1-Propanol CH3CH2CH2OH 97Hydrogen bonding



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• Aldehydes and ketones can form weak hydrogen bonds between the carbonyl oxygen and the hydrogen atoms of water.

– The lower members of the series—up to three carbons—are soluble in water in all proportions.

– As the length of the hydrocarbon chain increases above four, however, water solubility decreases.

• As might be expected, all aldehydes and ketones are soluble in nonpolar solvents.


Properties of Aldehydes and Ketones



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Why do aldehydes and ketones have similar properties?



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Why do aldehydes and ketones have similar properties?

Aldehydes and ketones have similar properties because each contains a C O functional group.



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Carboxylic Acids

What is the general formula of a carboxylic acid?

Carboxylic AcidsCarboxylic Acids



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• A carboxyl group is a functional group that consists of a carbonyl group attached to a hydroxy group.

– It can be written as —COOH or —CO2H.

• A carboxylic acid is an organic compound with a carboxyl group.




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The general formula of a carboxylic acid is RCOOH.




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• In water, they can lose a hydrogen ion and form a carboxylate ion, as shown in the following reaction.


Carboxylic acids are considered weak acids because they ionize weakly in solution.



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• Remember, the parent hydrocarbon of a carboxylic acid is the longest continuous carbon chain containing the carboxyl group.

• The carboxylic acid CH3COOH is named ethanoic acid.


In the IUPAC system, carboxylic acids are named by replacing the -e ending of the parent structure with the ending -oic acid.



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Some Saturated Aliphatic Carboxylic Acids

Molecular formula

Carbon atoms

IUPAC nameCommon

nameMelting

point (°C)

HCOOH 1 Methanoic acid Formic acid 8

CH3COOH 2 Ethanoic acid Acetic acid 17

CH3CH2COOH 3 Propanoic acid Propionic acid –22

CH3(CH2)2COOH 4 Butanoic acid Butyric acid –6

CH3(CH2)4COOH 6 Hexanoic acid Caproic acid –3

CH3(CH2)6COOH 8 Octanoic acid Caprylic acid 16

CH3(CH2)8COOH 10 Decanoic acid Capric acid 31

CH3(CH2)10COOH 12 Dodecanoic acid Lauric acid 44

CH3(CH2)12COOH 14 Tetradecanoic acid Myristic acid 58

CH3(CH2)14COOH 16 Hexadecanoic acid Palmitic acid 63

CH3(CH2)16COOH 18 Octadecanoic acid Stearic acid 70



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Lemons and limes contain citric acid, a carboxylic acid that gives citrus fruits their sour flavor.




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Many carboxylic acids were first isolated from fats and are called fatty acids.


• Propionic acid, the three-carbon acid, literally means first fatty acid.



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Like alcohols, carboxylic acids form intermolecular hydrogen bonds.

• Thus, carboxylic acids have higher boiling and melting points than other compounds of similar molar mass.

• The low-molar-mass members of the aliphatic carboxylic acid series are colorless, volatile liquids.

• The higher members of the series are nonvolatile, waxy solids with low melting points.

• All aromatic carboxylic acids are solids at room temperature.




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The carboxyl group in carboxylic acids is polar and readily forms hydrogen bonds with water molecules.

• Methanoic, ethanoic, propanoic, and butanoic acids are completely soluble in water.

• After four carbons, however, the solubility drops sharply.

• Most carboxylic acids are also soluble in organic solvents such as ethanol or propanone.




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What is a fatty acid?



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What is a fatty acid?

A fatty acid is a carboxylic acid that was first isolated from fats.



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Oxidation-Reduction Reactions

Why is dehydrogenation classified as an oxidation reaction?

Oxidation-Reduction Oxidation-Reduction ReactionsReactions



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The classes of organic compounds you have just studied—aldehydes, ketones, and carboxylic acids—are related by oxidation and reduction reactions.

• Oxidation is the gain of oxygen, loss of hydrogen, or loss of electrons.

• Reduction is the loss of oxygen, gain of hydrogen, or gain of electrons.

• One does not occur without the other.




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In organic chemistry, the number of oxygen atoms and hydrogen atoms attached to carbon indicates the degree of oxidation of a compound.

• The fewer hydrogens on a carbon-carbon bond, the more oxidized the bond.

• Thus, a triple bond is more oxidized than a double bond, which is more oxidized than a single bond.




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The loss of a molecule of hydrogen from an organic molecule is called a dehydrogenation reaction.

• It is the opposite of a hydrogenation reaction.

• Strong heating and a catalyst are usually needed to make dehydrogenation reactions occur.




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Dehydrogenation is an oxidation reaction because the loss of each molecule of hydrogen involves the loss of two electrons from the organic molecule.


• The remaining carbon electrons pair to make a second or third bond.



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Oxidation in organic chemistry also involves the number and degree of oxidation of oxygen atoms attached to the carbon atom.


• Methane, a saturated hydrocarbon, can be oxidized in steps to carbon dioxide.

• Methane is oxidized to methanol, then to methanal, then to methanoic acid, and finally to carbon dioxide.



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• The oxidation of organic compounds is exothermic.

• The energy-releasing properties of oxidation reactions are extremely important for the production of energy in living systems.


The more reduced a carbon compound is, the more energy it can release upon its complete oxidation to carbon dioxide.



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Primary alcohols can be oxidized to aldehydes.




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Secondary alcohols can be oxidized to ketones by warming them with acidified potassium dichromate (K2Cr2O7).




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Tertiary alcohols, however, cannot be oxidized because there is no hydrogen atom present on the carbon atom attached to the hydroxy group.




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Aldehydes are so easily oxidized that it is difficult to prevent further oxidation to carboxylic acids.


• Further oxidation is avoided by removing aldehydes from the reaction mixture as they are formed.



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Tests for aldehydes make use of the ease with which these compounds are oxidized.


• Benedict’s and Fehling’s reagents are deep-blue alkaline solutions of copper(II) sulfate.

• When an aldehyde is oxidized with Benedict’s or Fehling’s reagent, a red precipitate of copper(I) oxide is formed.

• The aldehyde is oxidized to its acid, and copper (II) ions are reduced to copper(I) ions.



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What hydrocarbon can be oxidized to form aldehydes? What hydrocarbon can be oxidized to ketones?



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What hydrocarbon can be oxidized to form aldehydes? What hydrocarbon can be oxidized to ketones?

A primary alcohol can be oxidized to an aldehyde. A secondary alcohol can be oxidized to a ketone.



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Esters

What is the general formula of an ester?

EstersEsters



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Esters are probably the most pleasant and delicious organic compounds one can study.

• Many esters have pleasant, fruity odors.

• Esters give blueberries, pineapples, apples, pears, bananas, and many other fruits their characteristic aromas.

• They also give many perfumes their fragrances.

EstersEsters



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An ester is an organic compound in which the —OH of the carboxyl group has been replaced by an —OR from an alcohol.

• Esters contain a carbonyl group and an ether link to the carbonyl carbon.

EstersEsters



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The general formula of an ester is RCOOR.

EstersEsters



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The smell of strawberries is largely due to benzyl acetate. The smell of almonds is largely due to benzaldehyde. How are the general formulas of these compounds similar? How are they different?




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The smell of strawberries is largely due to benzyl acetate. The smell of almonds is largely due to benzaldehyde. How are the general formulas of these compounds similar? How are they different?


Benzyl acetate and benzaldehyde each contain a benzene ring. Benzyl acetate contains an ester group, while benzaldehyde contains an aldehyde group.



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Although ester molecules are polar, they cannot form hydrogen bonds with one another.

EstersEsters

• They do not contain hydrogen attached to oxygen or another electronegative atom.

• As a result, only weak attractions hold ester molecules to one another.



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EstersEsters

• They do not contain hydrogen attached to oxygen or another electronegative atom.

• As a result, only weak attractions hold ester molecules to one another.

– Esters have much lower boiling points than carboxylic acids.



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EstersEsters

• The low-molar-mass esters are somewhat soluble in water, but esters containing more than four or five carbons have very limited solubility.



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Esters may be prepared from a carboxylic acid and an alcohol.

• The process is called esterification.

• The reactants, usually a carboxylic acid and a primary or secondary alcohol, are heated with an acid as a catalyst.

EstersEsters



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If an ester is heated with water for several hours, usually very little happens.

• In strong acid or base solutions, however, the ester breaks down.

• An ester is hydrolyzed by the addition of water to produce a carboxylic acid and an alcohol.

EstersEsters



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Hydroxide ions also promote this reaction.

EstersEsters

• Because many esters do not dissolve in water, a solvent such as ethanol is added to make the solution homogeneous.

• The reaction mixture is usually heated.

• All of the ester is converted to products.



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If the reaction mixture is acidified, the carboxylic acid forms.

EstersEsters



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What are reactants in an esterification reaction? What are the products?



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What are reactants in an esterification reaction? What are the products?

The reactants in an esterification reaction are a carboxylic acid and an alcohol. The products are an ester and water.



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Key ConceptsKey Concepts

The C O functional group is present in aldehydes and ketones.

The general formula of a carboxylic acid is RCOOH.

Dehydrogenation is an oxidation reaction because the loss of each molecule of hydrogen involves the loss of two electrons from the organic molecule.

The general formula of an ester is RCOOR.



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• carbonyl group: a functional group having a carbon atom and an oxygen atom joined by a double bond; it is found in aldehydes, ketones, esters, and amides

• aldehyde: an organic compound in which the carbon of the carbonyl group is joined to at least one hydrogen; the general formula is RCHO

• ketone: an organic compound in which the carbon of the carbonyl group is joined to two other carbons; the general formula is RCOR

Glossary TermsGlossary Terms



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• carboxyl group: a functional group consisting of a carbonyl group attached to a hydroxyl group; it is found in carboxylic acids

• carboxylic acid: an organic acid containing a carboxyl group; the general formula is RCOOH

• fatty acid: the name given to continuous-chain carboxylic acids that were first isolated from fats




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• dehydrogenation reaction: a reaction in which hydrogen is lost

• ester: a derivative of a carboxylic acid in which the —OH of the carboxyl group has been replaced by the —OR from an alcohol; the general formula is RCOOR




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• Chemical reactions can be used to change the structure of organic molecules, often by introducing a new functional group.

• Oxidation-reduction reactions are commonly used in organic chemistry.

BIG IDEABIG IDEA

Carbon Chemistry and Reactions



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END OF 23.3END OF 23.3

23.3 carbonyl compounds > 1 copyright © pearson education, inc., or its affiliates. all rights...

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