Esters ethers ketones identifying groups
Ketone Ketones have a pair of alkyl or aromatic groups attached to a carbonyl function. Ketones give red-orange precipitates with 2,4-dinitrophenyl hydrazine. Carboxylic acid Carboxylic acids have an alkyl or aromatic groups attached to a hydroxy-carbonyl function. Amide Primary amides shown have an alkyl or aromatic group attached to an amino-carbonyl function. Primary amines can be shown in text as: RNH2 Primary amines are basic functions that can be protonated to the corresponding ammonium ion.
Primary amines are also nucleophilic. Secondary amine Secondary amines have a pair of alkyl or aromatic groups, and a hydrogen, attached to a nitrogen atom. Secondary amines can be shown in text as: R2NH Secondary amines are basic functions that can be protonated to the corresponding ammonium ion.
Secondary amines are also nucleophilic. Tertiary amine Tertiary amines have three alkyl or aromatic groups attached to a nitrogen atom. Tertiary amines can be shown in text as: R3N Tertiary amines are basic functions that can be protonated to the corresponding ammonium ion. Tertiary amines are also nucleophilic. Nitrile Nitriles or organo cyanides have an alkyl or aromatic group attached to a carbon-triple-bond-nitrogen function.
If a compound is named as the nitrile then the nitrile carbon is counted and included, but when the compound is named as the cyanide it is not. Carboxylate ion or salt Carboxylate ions are the conjugate bases of carboxylic acids, ie. Carboxylate ions can be shown in text as: RCOO— When the counter ion is included, the salt is being shown.
Salts can be shown in text as: RCOONa Amino acid Amino acids, strictly alpha-amino acids, have carboxylic acid, amino function and a hydrogen attached to a the same carbon atom. There are 20 naturally occurring amino acids. Alkenes are electron rich reactive centres and are susceptible to electrophilic addition. Ether Ethers have a pair of alkyl or aromatic groups attached to a linking oxygen atom.
Ethers can be shown in text as: ROR Ethers are surprisingly unreactive and are very useful as solvents for many many but not all classes of reaction. From Mark R. Leach The R represents a carbon based group. The carbonyl group can attach to two other substituents leading to several subfamilies, some of which are: aldehydes, ketones, carboxylic acids, esters and amides. Naming of Aldehydes and Ketones Both aldehydes and ketones contain a carbonyl group. In an aldehyde, the carbonyl group is bonded to at least one hydrogen atom.
In a ketone, the carbonyl group is bonded to two carbon atoms. The names for aldehyde and ketone compounds are derived using similar nomenclature rules as for alkanes and alcohols, and include the class-identifying suffixes -al and -one, respectively: Therefore when naming aldehydes following IUPAC, you follow these rules: Rule 1. And when numbering the parent chain, the carbonyl group gets the lowest possible number, therefore it is always 1 and therefore is not included in the name.
Rule 2. Names and position of the substituents. Methanal has a common name with which you may be familiar: formaldehyde.
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Aldehydes and Ketones Both aldehydes and ketones contain a carbonyl group, a functional group with a carbon-oxygen double bond. The names for aldehyde and ketone compounds are derived using similar nomenclature rules as for alkanes and alcohols, and include the class-identifying suffixes -al and -one, respectively: In an aldehyde, the carbonyl group is bonded to at least one hydrogen atom. In a ketone, the carbonyl group is bonded to two carbon atoms: As text, an aldehyde group is represented as —CHO; a ketone is represented as —C O — or —CO—.
In both aldehydes and ketones, the geometry around the carbon atom in the carbonyl group is trigonal planar; the carbon atom exhibits sp2 hybridization. The carbonyl group is polar, and the geometry of the bonds around the central carbon is trigonal planar.
The importance of molecular structure in the reactivity of organic compounds is illustrated by the reactions that produce aldehydes and ketones. We can prepare a carbonyl group by oxidation of an alcohol—for organic molecules, oxidation of a carbon atom is said to occur when a carbon-hydrogen bond is replaced by a carbon-oxygen bond. The reverse reaction—replacing a carbon-oxygen bond by a carbon-hydrogen bond—is a reduction of that carbon atom. Recall that oxygen is generally assigned a —2 oxidation number unless it is elemental or attached to a fluorine.
Since carbon does not have a specific rule, its oxidation number is determined algebraically by factoring the atoms it is attached to and the overall charge of the molecule or ion. In general, a carbon atom attached to an oxygen atom will have a more positive oxidation number and a carbon atom attached to a hydrogen atom will have a more negative oxidation number.
This should fit nicely with your understanding of the polarity of C—O and C—H bonds. The other reagents and possible products of these reactions are beyond the scope of this chapter, so we will focus only on the changes to the carbon atoms: Oxidation and Reduction in Organic Chemistry Methane represents the completely reduced form of an organic molecule that contains one carbon atom. 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.
Check Your Learning Indicate whether the marked carbon atoms in the three molecules here are oxidized or reduced relative to the marked carbon atom in ethanol: There is no need to calculate oxidation states in this case; instead, just compare the types of atoms bonded to the marked carbon atoms: Answer: a reduced bond to oxygen atom replaced by bond to hydrogen atom ; b oxidized one bond to hydrogen atom replaced by one bond to oxygen atom ; c oxidized 2 bonds to hydrogen atoms have been replaced by bonds to an oxygen atom Aldehydes are commonly prepared by the oxidation of alcohols whose —OH functional group is located on the carbon atom at the end of the chain of carbon atoms in the alcohol: Alcohols that have their —OH groups in the middle of the chain are necessary to synthesize a ketone, which requires the carbonyl group to be bonded to two other carbon atoms: 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.
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.
Carboxylic Acids and Esters 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.
Figure 2. Esters are responsible for the odors associated with various plants and their fruits. 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 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.
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. Pure acetic acid has a penetrating odor and produces painful burns.
It is an excellent solvent for many organic and some inorganic compounds, and it is essential in the production of cellulose acetate, a component of many synthetic fibers such as rayon. The distinctive and attractive odors and flavors of many flowers, perfumes, and ripe fruits are due to the presence of one or more esters Figure 3.
Palmitic and stearic acids are saturated acids that contain no double or triple bonds. Figure 3. Over different volatile molecules many members of the ester family have been identified in strawberries. The carbonyl group, a carbon-oxygen double bond, is the key structure in these classes of organic molecules: Aldehydes contain at least one hydrogen atom attached to the carbonyl carbon atom, ketones contain two carbon groups attached to the carbonyl carbon atom, carboxylic acids contain a hydroxyl group attached to the carbonyl carbon atom, and esters contain an oxygen atom attached to another carbon group connected to the carbonyl carbon atom.
All of these compounds contain oxidized carbon atoms relative to the carbon atom of an alcohol group. 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?