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Introduction
Compounds seen in liquid, solid or gaseous states that contain carbon in their molecules are referred to as organic compounds. These compounds can be seen in multiple formats, including space-filled models, Lewis structures, and structural formulas.
Carbonyl group is a prominent class of molecules coming under organic chemistry. It features a carbon (C) atom that is connected to an oxygen (O2) atom by a double bond. This is popularly known as a carbonyl group. Trigonal planar carbon in this group can get attached to 2 other substituents, subsequently leading to multiple subfamilies. These subfamilies are ketones, aldehydes, esters and carboxylic acids.
Aldehydes and Ketones
Ketones and aldehydes contain one carbonyl group, which is a functional group having a carbon-oxygen double bond. The carbonyl group is bonded with at least a single hydrogen atom, while it is bonded to two carbon atoms in a ketone. Ketone essentially is represented as –C(O)– or –CO– and an aldehyde group is represented as –CHO.
In both ketones and aldehydes, the geometry around the carbon atom in the carbonyl group is known as the trigonal planar. sp2 hybridization is exhibited by carbon atoms. 2 of the sp2 orbitals on carbon atoms in the carbonyl group tend to form σ bonds to any other hydrogen or carbon atoms present in a molecule.
The residual sp2 hybrid orbital forms a σ bond to the oxygen atom, while the unhybridized p orbital present on the carbon atom in the carbonyl group tends to overlap a p orbital on the oxygen atom for forming the π bond in the double bond.
Similar to the C=O bond in carbon dioxide, the C=O bond of a carbonyl group is polar. A lot of reactions of ketones and aldehydes begin with the reaction between the carbon atom and Lewis base. This happens at the positive end of the polar C=OC=O bond.
The significance of molecular structure in terms of reactivity of organic compounds has been featured by the reactions that end up producing ketones and aldehydes. The Carbonyl group can be prepared with the help of the oxidation of alcohol.
Oxidation of carbon atoms typically occurs when a carbon-oxygen bond replaces a carbon-hydrogen bond. On the other hand, a reverse reaction of a carbon-hydrogen bond replacing a carbon-oxygen bond essentially is a lessening of that carbon atom.
Oxygen is typically assigned a –2 oxidation numeral until it is attached to fluorine or is elemental. Hydrogen tends to be assigned an oxidation number of +1 if it is not linked to a metal. If carbon doesn’t have a particular rule, the oxidation numeral is selected algebraically by opting to factor in the atoms that are linked to the overall charge of the ion or molecule.
On the whole, a carbon atom linked to an oxygen atom would have a superior positive oxidation numeral, while a carbon atom linked to a hydrogen atom shall have a more negative oxidation numeral.
Carboxylic Acids
Carboxylic acid functional groups that contain a carboxyl functional group, –COOH are known as carboxylic acids. Carboxylic acids can be aromatic (ArCOOH) or aliphatic (RCOOH), depending on the aryl or alkyl attached to carboxylic carbon.
A good number of carboxylic acids can be found in nature itself. A few higher members of aliphatic carboxylic acids are called fatty acids. They occur in natural fats in the form of esters of glycerol. Carboxylic acids serve as a starting material for multiple other organic compounds like amides, acid chlorides, anhydrides, esters, etc.
As carboxylic acids tend to be one of the earliest organic compounds to be isolated from nature, many of them are known by their common names. The carboxylic carbon is numbered one when it comes to numbering the carbon chain.
Esters
Esters are derived from the reaction of a carboxylic acid with alcohol. Amino acid esters subsequently refer to the derivatives of amino acids in which the carboxylic acid functional group gets converted to an ester.
Amino group esters are essentially employed as intermediates in organic synthesis. They are known to find application in many areas, from peptide synthesis and medicinal chemistry to asymmetric synthesis and polymer chemistry.
Esters that contain long alkyl chains (R) mainly constitute vegetable and animal oils and fats. Several esters feature small alkyl chains that are fruity in smell and, therefore, commonly used in fragrances.
Both esters and carboxylic acids contain a carbonyl group with a second oxygen atom. This atom is bonded to the carbon atom in the carbonyl group by a single bond. Conversely, In a carboxylic acid, the second oxygen atom also has a bond with a hydrogen atom.
On the other hand, the second oxygen atom bonds to another carbon atom in an ester. The names of esters and carboxylic acids tend to consist of prefixes that effectively indicate the carbon chain length in molecules. They are the result of nomenclature rules comparable to the ones associated with salts and inorganic acids.
Weak acids like Carboxylic acids are not fully ionized in water. Typically, only one percent of carboxylic acid molecules that are dissolved in H2O are ionized at a single point in time. In contrast, the remaining ones are un-dissociated in solution.
Carboxylic acids are prepared by the oxidation of alcohols or aldehydes whose –OH functional group tends to be present on carbon atoms right at the end of the chain of carbon atoms in alcohol.
Conclusion
Aldehydes, ketones, and carboxylic acids are a few of the most important classes of organic compounds that contain carbonyl groups. These are extremely polar molecules and hence boil at higher temperatures in comparison to weakly polar compounds like ethers of comparable molecular masses.
Ketones feature two carbon groups attached to the carbonyl carbon atom, aldehydes contain at least a single hydrogen atom attached to the carbonyl carbon atom, while carboxylic acids contain a hydroxyl group attached to the carbonyl carbon atom. Esters feature an oxygen atom attached to another carbon group connected to the carbonyl carbon atom. The nomenclature of Aldehydes, ketones, and carboxylic acids can be done by following IUPAC guidelines or by following common practices.
