What is a Carboxyl Group?
A carboxyl group is a very common functional group that is defined as having a carbonyl and hydroxyl group linked to a carbon atom through a single bond. Similarly, an organic compound containing a carboxyl group is referred to as a carboxylic acid. Just to remember, a carbonyl group is a carbon double-bonded to oxygen, and a hydroxyl group is an OH group.
While working with a carboxyl group, we need to be on the lookout for two things: a carbon and an OH double-bonded to oxygen. But, better, if we consider the word carboxyl, we can split it down into two parts as 'carb' and 'oxyl.' Seeing 'carb,' we think of the carbon atom. Whereas, seeing '-oxyl,' we think about the hydroxyl group. On the other hand, COOH is the molecular formula for a carboxyl group.
Carboxyl Group Examples
One of the best-known carboxyl group examples from carbon molecules is a carboxylic acid. The carboxylic acid’s general formula is R-C(O)OH. Where R defines any number of chemical species. Carboxylic acids are found in amino acids and acetic acids that are used to build proteins.
Because the hydrogen ion detaches behavior so readily, most commonly, the molecule is found as a carboxylate anion R-COO-. With the help of the suffix “-ate,” the anion is named. For example, acetic acid (a carboxylic acid) becomes an acetate ion.
Carboxyl Group Formula
Carboxylic acids are a homologous series where the compounds contain a functional group known as a carboxyl group (-COOH). The general carboxyl group molecular formula will be, \[CnH_{2}n+1COOH\]. Carboxylic acids contain a minimum of one carboxyl group. The acids with two or more carboxyl groups attached are referred to as dicarboxylic acids, tricarboxylic acids, and so on. Also, carboxylic acids are the derivatives of hydrocarbons where a carboxyl group has replaced one or more to that of the hydrogen atoms in the hydrocarbon. The carboxylic acids (first four) derived from alkanes are ethanoic acid (\[CH_{3}COOH\].), methanoic acid (HCOOH), propanoic acid (\[C_{2}H_{5}COOH\].), and butanoic acid (\[C_{3}H_{7}COOH\].).
The carboxyl group structure for all the above-mentioned carboxylic acids is given below.
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Nomenclature of Carboxylic Acids
If either the compound or the primary carbon skeleton is acyclic, name the alkane for the system that would occur if the carboxylic acid were a \[CH_{3}\] group. Then drop the terminal ‘-e’ by substituting “-oic” acid. The carbon present in the carboxylic acid group is always carbon 1 (this can make different numbers from that of the alkane).
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If the other structural feature overrides the carboxylic acid (suppose, a ring), a suffix “-carboxylic” acid will be added to a root name taken by excluding the carbon atom of carboxylic acid. The carboxylic acid again defines the numbering, but now C-1 is the carbon, bearing with the COOH group.
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Structure of Carboxyl Group
Carboxyl groups exists on the side of a molecule. It ionizes, discharging the Hydrogen (H) from the hydroxyl aggregate as a free proton (H+), with the rest of the Oxygen (O) conveying a negative (-ve) charge. This charge turns forward and backward between the two oxygen molecules, which makes this ionized state steady moderately.
The 3D ball structure of a carboxyl group is represented below.
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Properties of Carboxyl Group
Few of the properties of the carboxyl group are listed below:
The Carboxyl group contains a double bond of electronegative oxygen to a carbon atom. As a result, the polarity of a bond will increase.
A compound containing a carboxyl group should possess hydrophilic centers with a high melting point and boiling point.
The reason behind the high melting and boiling point may be dissipated by creating a hydrogen bond in the solid-state and liquid state. Another typical example is fatty acids.
Carboxyl Group from Nature
Acetic acid can be naturally blended by anaerobic fermentation, which is the procedure used to produce vinegar. The rigorous approach includes warm ethanol and Acetobacter oxygen. The anaerobic process requires only sugar as an input chemical, and acetogen will then yield carboxylic acids. It should be noticed that the high-impact process is still mostly connected because the acetogenins are utilized for anaerobic procedures by indicating less resistance to acidic situations. Ultimately, acetogenesis will be destroyed if a large quantity of acids is produced to a great volume.
Benzoic acid is a fundamental element of benzoin resin. Genuinely, it is expensive to remove benzoic acid, primarily from benzoin resins. Most of the benzoic acid found in the market is manufactured mechanically along these lines.
Uses of Carboxylic Acids
Methanoic is the acid used in rubber, textile, dyeing, leather, and electroplating industries.
Acetic acid is used as a solvent and as vinegar in the food industry.
Hexanedioic acid is used in the manufacturing of nylon-6, 6, which is a commercially important polymer.
Esters of benzoic acid are used in perfume-making industries.
Sodium Benzoate is also used as a preservative.
Higher fatty acids are used in the manufacturing of detergents and soaps.
Did you know?
Carboxylic groups form bonds with each other due to their tendency to be stable in dimers
Acids participate in hydrogen bonding actively
Quick Summary
Tips & Trick to learn this Concept:
Organic concept and organic chemistry overall constitute a heavier weightage in chemistry as compared to inorganic chemistry.
It might seem difficult to learn at first glance but if studied thoroughly with practice, organic chemistry is good for scoring in exams.
The most important advice to study organic chemistry is not to learn it but to understand it
If any student is starting organic chemistry then he/ she must first start with the basic concepts. This followed by learning the nomenclature of the groups present in that compound, IUPAC names, and how to name them.
Later applications, synthesis, physical and chemical properties can be studied.
However, this studying must not be limited to just once, but until and unless the subject reaches a confident level, then these steps must be repeated while revising the subject.
The Acidity of Carboxylic Acids:
Carboxylic acid is the group of acids ranging from any number of compounds containing carbon and hydroxyl groups from any of the organic groups.
However Carboxylic acids are weak acids and they only partially dissociate into cations and anions.
The most acidic carboxylic acid is acetic acid followed by Benzoic acid and formic acid.
This list continues until trichloroacetic acid and trifluoroacetic acid.
Expected Questions
What is a carboxylic acid and how is it made?
Explain the physical properties of carboxylic acids.
Explain the chemical properties of carboxylic acids.
What are the uses of carboxylic acid?
What is the acidity of a carboxylic acid?
Explain amino acids in detail.
Does carboxylic acid have resonance structures?
FAQs on Carboxyl Group
1. Why are carboxylic acids more acidic than phenol?
The acidity of a carboxylic acid is higher compared to alcohol and phenols because, carboxylate ion, the conjugate base of the carboxylic acid is stabilized by two equivalent resonance structures where the negative charge is effectively delocalized between two more electronegative oxygen atoms.
On the other side, considering phenols, a negative charge is delocalized less strongly on one oxygen atom and also less electronegative carbon atoms in phenoxide ions. The carboxylate ion is, therefore, more stable compared to the phenoxide ion. Carboxylic acids are also more acidic than phenols.
2. Why are carboxylic acids stronger acids compared to alcohol?
It is because of electronegativity. For Bronsted acids (such as alcohols and carboxylic acids), an acid is stronger when its tendency to release a proton is strong.
For both carboxylic acid and alcohol, there is hydrogen covalently bound to oxygen (but not exactly true because for the carboxylic acid, the bond is spread out between the two oxygens).
Also, oxygen is more electronegative than hydrogen. It means that oxygen is an electron-withdrawing. If we withdraw the electrons from the covalent bond to hydrogen, we get a hydrogen ion (which is a proton).
To make it simple, because two oxygens (carboxylic acid) are more electron-withdrawing than one oxygen (alcohol), generally, they have a larger tendency to “release” the proton, i.e., they are stronger acids.
3. What elements are there in the carboxyl group?
The Carboxyl group consists of carbon having Bonded with oxygen and hydroxyl group. The Carboxyl group is attached to some other elements. The compound formed gives many properties. Carboxyl groups are often seen in organic elements such as Carboxylic acids. The Carboxyl group can be presented as RCOOH. Where R can take any compound or element containing carbons. In this form of carboxylic group structure, the carbon is bonded with oxygen via the double bond and with hydroxyl group i.e. OH, via a single bond. Examples of Carboxylic acids include amino acids, fatty acids, keto acids, and many more.
4. What is a carboxyl group protein?
Carboxyl groups are formed by the combination of two groups that are of hydroxyl and carbonyl. The carboxyl group is made up of one carbon and two oxygens denoted by COO-. There are proteins present in carboxyl groups named amino acids. Amino acids are built and used in every part of the human body to provide protein. Protein is required for various uses from daily life processes to cellular functions. Amino acids have two carbon bonds one of which has a carboxyl group. And another carbon is connected to the amino groups. These acids bond together with each other to make long chains. And these long chains give rise to proteins. Scientists have discovered over 50 amino acids but we only use 20 acids out of them which are essential proteins required for the body.
5. What are the different types of carboxylic acids?
Carboxylic acids are organic acids containing carboxyl groups. There are different types of carboxylic acids such as
Alkanoic Acids: Alkanoic acids are straight-chain saturated acids that form the very basic carbocyclic acid. Alkanoic acid starts from single hydrogen with the carboxylic group giving methanoic acid to acid containing 20 carbons named arachidic acid.
Fatty Acids: Fatty acids are saturated acids with medium to long length chains. These acids contain an even number of carbons and are used as natural supplements.
Amino Acids: Amino Acids are building blocks for proteins. Along with the carboxyl group, the amino group is attached and hence amino acid is formed. The structure bonds with itself to form a long chain resulting in proteins.
Keto Acids: Keto acids are the acids that contain a Ketone group along with a carboxyl group. Examples are acetoacetic acid and pyruvic acid.
Aromatic Carboxylic Acids: These carboxylic acids contain at least 1 aromatic compound attached to the carboxyl group.. Examples of aromatic Carboxylic acids are salicylic acid, Benzoic acid.
Dicarboxylic Acids: These acids contain two carboxyl groups present in the compound. Examples of dicarboxylic acids are Adipic Acid. Adipic acid is the monomer used to produce nylon.
Tricarboxylic Acids: Tricarboxylic acids are acids that contain three carboxyl groups. Examples of these include citric acid, found in Citrus Fruits.