Carboxyl Group Structure Properties and Chemical Behavior

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

1. What is a carboxylic acid and how is it made?

2.  Explain the physical properties of carboxylic acids.

3.  Explain the chemical properties of carboxylic acids.

4.  What are the uses of carboxylic acid?

5.  What is the acidity of a carboxylic acid?

6.  Explain amino acids in detail.

7.  Does carboxylic acid have resonance structures?