All of these compounds contain oxidized carbon atoms relative to the carbon atom of an alcohol group. A ketone contains a group bonded to two additional carbon atoms; thus, a minimum of three carbon atoms are needed.
Since they are both carboxylic acids, they each contain the —COOH functional group and its characteristics. The difference is the hydrocarbon chain in a saturated fatty acid contains no double or triple bonds, whereas the hydrocarbon chain in an unsaturated fatty acid contains one or more multiple bonds.
Skip to main content. Module Organic Chemistry. Search for:. Aldehydes, Ketones, Carboxylic Acids, and Esters Learning Outcomes Describe the structure and properties of aldehydes, ketones, carboxylic acids, and esters. Example 1: Oxidation and Reduction in Organic Chemistry Methane represents the completely reduced form of an organic molecule that contains one carbon atom.
Show Solution In this example, we can calculate the oxidation number review the chapter on oxidation-reduction reactions if necessary for the carbon atom in each case note how this would become difficult for larger molecules with additional carbon atoms and hydrogen atoms, which is why organic chemists use the definition dealing with replacing C—H bonds with C—O bonds described.
Show Solution reduced bond to oxygen atom replaced by bond to hydrogen atom oxidized one bond to hydrogen atom replaced by one bond to oxygen atom oxidized 2 bonds to hydrogen atoms have been replaced by bonds to an oxygen atom.
Try It Order the following molecules from least to most oxidized, based on the marked carbon atom: Predict the products of oxidizing the molecules shown in this problem. In each case, identify the product that will result from the minimal increase in oxidation state for the highlighted carbon atom: Predict the products of reducing the following molecules.
In each case, identify the product that will result from the minimal decrease in oxidation state for the highlighted carbon atom: Explain why it is not possible to prepare a ketone that contains only two carbon atoms. How does hybridization of the substituted carbon atom change when an alcohol is converted into an aldehyde? An aldehyde to a carboxylic acid? Fatty acids are carboxylic acids that have long hydrocarbon chains attached to a carboxylate group.
How does a saturated fatty acid differ from an unsaturated fatty acid? How are they similar? Write a condensed structural formula, such as CH 3 CH 3 , and describe the molecular geometry at each carbon atom.
Draw the Lewis structure and determine the oxidation number and hybridization for each carbon atom in the molecule. The esters formed from butyric acid are pleasant-smelling compounds found in fruits and used in perfumes.
Draw the Lewis structure for the ester formed from the reaction of butyric acid with 2-propanol. Write the two-resonance structures for the acetate ion. Write two complete, balanced equations for each of the following reactions, one using condensed formulas and one using Lewis structures: ethanol reacts with propionic acid benzoic acid, C 6 H 5 CO 2 H, is added to a solution of sodium hydroxide Write two complete balanced equations for each of the following reactions, one using condensed formulas and one using Lewis structures.
What is the percent yield of a process that produces Molecules of alcohol A contain a branched carbon chain and can be oxidized to an aldehyde; molecules of alcohol B contain a linear carbon chain and can be oxidized to a ketone; and molecules of alcohol C can be oxidized to neither an aldehyde nor a ketone. Write the Lewis structures of these molecules. Show Selected Solutions 2. The products are as follows: 4. An alcohol with its —OH group bonded to a carbon atom that is bonded to no or one other carbon atom will form an aldehyde.
An alcohol with its —OH group attached to two other carbon atoms will form a ketone. If three carbons are attached to the carbon bonded to the —OH, the molecule will not have a C—H bond to be replaced, so it will not be susceptible to oxidation. Formaldehyde, an aldehyde with the formula HCHO, is a colorless gas with a pungent and irritating odor. Formaldehyde causes coagulation of proteins, so it kills bacteria and any other living organism and stops many of the biological processes that cause tissue to decay.
Thus, formaldehyde is used for preserving tissue specimens and embalming bodies. It is also used to sterilize soil or other materials. Formaldehyde is used in the manufacture of Bakelite, a hard plastic having high chemical and electrical resistance.
It is made commercially by fermenting corn or molasses, or by oxidation of 2-propanol. Acetone is a colorless liquid. Among its many uses are as a solvent for lacquer including fingernail polish , cellulose acetate, cellulose nitrate, acetylene, plastics, and varnishes; as a paint and varnish remover; and as a solvent in the manufacture of pharmaceuticals and chemicals.
The odor of vinegar is caused by the presence of acetic acid, a carboxylic acid, in the vinegar. The odor of ripe bananas and many other fruits is due to the presence of esters, compounds that can be prepared by the reaction of a carboxylic acid with an alcohol. Because esters do not have hydrogen bonds between molecules, they have lower vapor pressures than the alcohols and carboxylic acids from which they are derived see Figure 2.
Both carboxylic acids and esters contain a carbonyl group with a second oxygen atom bonded to the carbon atom in the carbonyl group by a single bond. In a carboxylic acid, the second oxygen atom also bonds to a hydrogen atom.
In an ester, the second oxygen atom bonds to another carbon atom. The names for carboxylic acids and esters include prefixes that denote the lengths of the carbon chains in the molecules and are derived following nomenclature rules similar to those for inorganic acids and salts see these examples :.
The functional groups for an acid and for an ester are shown in red in these formulas. The hydrogen atom in the functional group of a carboxylic acid will react with a base to form an ionic salt:. The remaining molecules are undissociated in solution. We prepare carboxylic acids by the oxidation of aldehydes or alcohols whose —OH functional group is located on the carbon atom at the end of the chain of carbon atoms in the alcohol:.
Esters are produced by the reaction of acids with alcohols. The simplest carboxylic acid is formic acid, HCO 2 H, known since It is partially responsible for the pain and irritation of ant and wasp stings, and is responsible for a characteristic odor of ants that can be sometimes detected in their nests. Cider vinegar is produced by allowing apple juice to ferment without oxygen present. Yeast cells present in the juice carry out the fermentation reactions. The fermentation reactions change the sugar present in the juice to ethanol, then to acetic acid.
Most other common aldehydes are liquids at room temperature. Although the lower members of the homologous series have pungent odors, many higher aldehydes have pleasant odors and are used in perfumes and artificial flavorings. As for the ketones, acetone has a pleasant odor, but most of the higher homologs have rather bland odors. The solubility of aldehydes is therefore about the same as that of alcohols and ethers.
Formaldehyde, acetaldehyde, and acetone are soluble in water. As the carbon chain increases in length, solubility in water decreases. The borderline of solubility occurs at about four carbon atoms per oxygen atom. All aldehydes and ketones are soluble in organic solvents and, in general, are less dense than water. Aldehydes and ketones are much alike in many of their reactions, owing to the presence of the carbonyl functional group in both.
They differ greatly, however, in one most important type of reaction: oxidation. Aldehydes are readily oxidized to carboxylic acids, whereas ketones resist oxidation.
The aldehydes are, in fact, among the most easily oxidized of organic compounds. They are oxidized by oxygen O 2 in air to carboxylic acids. The ease of oxidation helps chemists identify aldehydes. A sufficiently mild oxidizing agent can distinguish aldehydes not only from ketones but also from alcohols.
Although ketones resist oxidation by ordinary laboratory oxidizing agents, they undergo combustion, as do aldehydes. Formaldehyde has an irritating odor. Because of its reactivity, it is difficult to handle in the gaseous state. Formaldehyde denatures proteins, rendering them insoluble in water and resistant to bacterial decay. For this reason, formalin is used in embalming solutions and in preserving biological specimens.
Aldehydes are the active components in many other familiar substances.
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