Let’s know about Carboxyl Group or Carboxylic Acid. A carboxylic acid is an organic acid that contains a carboxyl group (C(=O)OH) [1] attached to an R-group. The general formula for carboxylic acids is R-COOH or R-CO 2H , with R referring to the alkyl , alkyl , aryl , or other group . Carboxylic acids occur widely. Important examples include amino acids and fatty acids . The precipitation of a carboxylic acid gives a carboxylate ion.
Examples and Nomenclature
Carboxylic acids are usually identified by their trivial names . They often have the suffix -ic acid .IUPAC -recommended names also exist; In this system, the carboxylic acid has a -oic acid suffix. [2] For example, butyric acid (C 3 H 7 CO 2 H) is butyric acid according to IUPAC guidelines. For the nomenclature of complex molecules containing carboxylic acids, the carboxyl can be considered as one of the basic chains , even though there are other substitutes such as 3-chloropropanoic acid . Alternatively, it may be designated as a “carboxy” or “carboxylic acid” substituent on another basic structure such as 2-carboxyfuran .
The carboxylate ion (R – COO- or RCO 2 – ) of a carboxylic acid is usually designated with the suffix -ate, in keeping with the general pattern of -ic acid and -ate for a conjugate acid and its conjugate base . Keeping. For example, the conjugate base of acetic acid is acetate. Carbonic acid , which occurs in nature in bicarbonate buffer systems , is not usually classified as one of the carboxylic acids, despite it having a fraction that resembles a COOH group.
| carbon atom | common name | IUPAC name | chemical formula | common place or use |
|---|---|---|---|---|
| 1 | formic acid | methanoic acid | HCOOH | insect stings |
| 2 | vinegar acid | ethanoic acid | ch 3 kuh | vinegar |
| 3 | propionic acid | propanoic acid | CH 3 CH 2 COOH | Preservative for stored grains, body odor , milk, butter, cheese |
| 4 | butyric acid | butanoic acid | CH 3 (CH 2 ) 2 COOH CO | butter |
| 5 | valeric acid | pentanoic acid | CH 3 (CH 2 ) 3 COOH | valerian plant |
| 6 | caproic acid | hexanoic acid | CH 3 (CH 2 ) 4 COOH | goat fat |
| 7 | enanthic acid | heptanoic acid | CH 3 (CH 2 ) 5 COOH | Fragrance |
| 8 | caprylic acid | octanoic acid | CH 3 (CH 2 ) 6 COOH | Coconut |
| 9 | pelargonic acid | nonanoic acid | CH 3 (CH 2 ) 7 COOH | pelargonium plant |
| 10 | capric acid | decanoic acid | CH 3 (CH 2 ) 8 COOH | Coconut and Palm Kernel Oil |
| 1 1 | undecylenic acid | undecanoic acid | CH 3 (CH 2 ) 9 COOH | antifungal agent |
| 12 | lauric acid | dodecanoic acid | CH 3 (CH 2 ) 10 COOH | coconut oil and hand soap |
| १३ | tridecylic acid | tridecanoic acid | CH 3 (CH 2 ) 11 COOH | plant metabolite |
| 14 | myristic acid | tetradecanoic acid | CH 3 (CH 2 ) 12 COOH | nutmeg |
| 15 | pentadecylic acid | pentadecanoic acid | CH 3 (CH 2 ) 13 COOH | milk fat |
| 16 | palmitic acid | hexadecanoic acid | CH 3 (CH 2 ) 14 COOH | bribe |
| 17 | Margeric acid | heptadecanoic acid | CH 3 (CH 2 ) 15 COOH | pheromones in different animals |
| १८ | stearic acid | octadecanoic acid | CH 3 (CH 2 ) 16 COOH | Chocolate, wax, soap, and oil |
| 19 | nondecylic acid | nondecanoic acid | CH 3 (CH 2 ) 17 COOH | Fats, Vegetable Oils, Pheromones |
| 20 | arachidic acid | eicosanoic acid | CH 3 (CH 2 ) 18 COOH | peanut oil |
| compound class | members |
|---|---|
| unsaturated monocarboxylic acid | Acrylic acid (2-propanoic acid) – CH 2 =CHCOOH, used in polymer synthesis |
| fatty acids | Medium to long chain saturated and unsaturated monocarboxylic acids, with even numbers of carbons, e.g. docosahexaenoic acid and eicosapentaenoic acid (nutritional supplements) |
| amino acids | building blocks of proteins |
| keto acid | Acids of biochemical importance that contain a ketone group, e.g. acetoacetic acid and pyruvic acid |
| aromatic carboxylic acid | Containing at least one aromatic ring, examples: benzoic acid – the sodium salt of benzoic acid used as a food preservative, salicylic acid – a beta-hydroxy type found in many skin care products, phenyl alkanoic acid – class of compounds where a phenyl group is attached to a carboxylic acid |
| dicarboxylic acid | Adipic acid monomers containing two carboxyl groups, for example, used to produce nylon and aldaric acid – a family of sugar acids |
| tricarboxylic acid | Containing three carboxyl groups, eg: citric acid – found in citrus fruits and isocitric acid |
| alpha hydroxy acid | containing a hydroxy group, examples: glyceric acid, glycolic acid and lactic acid (2-hydroxypropanoic acid) – found in sour milk, tartaric acid – found in wine |
| Divinylether Fatty Acids | A doubly unsaturated carbon chain linked via an ether bond to a fatty acid found in some plants |
physical properties
solubility
Carboxylic acids are polar. Because they are both hydrogen-bond acceptors (carbonyl-C=O) and hydrogen-bond donors (hydroxyl-OH), they also participate in hydrogen bonding. The hydroxyl and carbonyl groups together form the functional group carboxyl. Carboxylic acids usually exist as dimers in non-polar media because of their tendency to “self-associate”. Smaller carboxylic acids (1 to 5 carbons) are soluble in water, whereas larger carboxylic acids have limited solubility due to the increasingly hydrophobic nature of the alkyl chain. These long-chain acids are soluble in less-polar solvents such as ether and alcohol. [3]Aqueous sodium hydroxide and carboxylic acids, even hydrophobic acids, react to generate water-soluble sodium salts. For example, acetic acid has a low solubility in water (0.2 g/L), but its sodium salt is very soluble in water.
boiling point
Carboxylic acids have higher boiling points than water, because of their greater surface area and their tendency to form stable dimers via hydrogen bonds. For boiling to occur, either the dimer bond must be broken or the entire dimer arrangement must be vaporized, greatly increasing the enthalpy of vaporization requirements.
acidity
Carboxylic acids are Brnsted–Lowry acids because they are proton (H + ) donors. They are the most common type of organic acid.
Carboxylic acids are generally weak acids, meaning that they only partially dissociate into H 3 O + cations and RCOO – anions in neutral aqueous solutions. For example, in a 1- molar solution of acetic acid, at room temperature, only 0.4% of the acid dissociates. Electron-withdrawing substances, such as the -CF group, give strong acids (formic acid has a pKa of 3.75 while trifluoroacetic acid, with a trifluoromethyl substituent, has a pK of 0.23 ). Electron-donating substituents give weak acids (formic acid has a pK A of 3.75 while acetic acid, with a methyl substitution, has a pK of 4.76).
| Carboxylic acid [4] | P K A |
|---|---|
| acetic acid (CH 3 CO 2 H) | 4.76 |
| Benzoic Acid ( C6H5CO2H ) _ _ | 4.2 |
| Formic Acid (HCOOH) | 3.75 |
| Chloroacetic acid (CH 2 ClCO 2 H) | 2.86 |
| Dichloroacetic acid (CHCl 2 CO 2 H) | १.२९ |
| Oxalic Acid (HO 2 CCO 2 H)(first separation) | 1.27 |
| Oxalic acid (HO 2 CCO 2 – )(second separation) | 4.14 |
| Trichloroacetic Acid (CCl 3 CO 2 H) | 0.65 |
| Trifluoroacetic acid (CF 3 CO 2 H) | 0.23 |
Precipitation of carboxylic acid gives carboxylate ion; These resonances are stable, because the negative charge is denoted on the two oxygen atoms, increasing the stability of the anion. Each carbon-oxygen bond in the carboxylate ion has a partial double-bond character. – The partial positive charge of the carbonyl carbon is also weaker than the negative charge on the 1 / 2 2 oxygen atoms.
‘odor
Carboxylic acids often have a strong sour smell. Esters of carboxylic acids have a pleasant odor, and many are used in perfumery.
characterization
Carboxylic acids are easily recognized by infrared spectroscopy. They exhibit a sharp band associated with the vibration of the Si–O vibrational bond (νC = O) between 1680 and 1725 cm . A characteristic OH band appears as a broad peak in the cm for 2500–3000–1 region . By 1 H NMR spectrometry, hydroxyl hydrogen appears in the 10–13 ppm region, although it is often observed either wide or not due to the exchange with traces of water.
Events and Applications
Many carboxylic acids are produced on a large scale industrially. They are also often found in nature. Esters of fatty acids are the main components of lipids and polyamides of aminocarboxylic acids are the main components of proteins.
Carboxylic acids are used in the production of polymers, pharmaceuticals, solvents, and food additives. Industrially important carboxylic acids include acetic acid (a component of vinegar, a precursor to solvents and coatings), acrylic and methacrylic acids (a precursor to polymers, adhesives), adipic acid (a polymer), citric acid (a flavoring in food and beverages). and protectors). Ethylenediaminetetraacetic acid (chelating agent), fatty acid (coating), malic acid (polymer), propionic acid (food preservative), terephthalic acid (polymer). The important carboxylate salts are soaps.
synthesis
industrial route
In general, the industrial routes of carboxylic acids differ from those used on a smaller scale because they require specialized equipment.
- Carbonylation of alcohols as shown by the Cativa process for the production of acetic acid. Formic acid is prepared by a different carbonylation pathway, also starting with methanol.
- Oxidation of aldehydes with air using cobalt and manganese catalysts. Essential aldehydes are readily obtained from alkanes by hydroformylation.
- Oxidation of hydrocarbons using air. For simple alkanes, this method is inexpensive but not selective enough to be useful. Allylic and benzylic compounds undergo more selective oxidation. The alkyl groups on the benzene ring are oxidized to carboxylic acids, regardless of its chain length. Benzoic acid to toluene, terephthalic acid to para -xylene, and phthalic acid to ortho -xylene are illustrative mass conversions. Acrylic acid is produced from propane. [5]
- Oxidation of ethene using silicotungstic acid catalyst.
- Base-catalyzed dehydrogenation of alcohols.
- Carbonylation coupled with the addition of water. This method is effective and versatile for alkenes that generate secondary and tertiary carbocations, for example from isobutylene to pivalic acid. In the Koch reaction, the addition of water and carbon monoxide to alkenes is catalyzed by strong acids. Hydrocarboxylation involves the simultaneous addition of water and CO. Such reactions are sometimes called “repe chemistry”.
HCCH + CO + H 2 O → CH 2 = CHCO 2 H
- Hydrolysis of triglycerides derived from plant or animal oils. These methods of synthesizing some long-chain carboxylic acids are related to soap making.
- Ethanol fermentation. This method is used in the production of vinegar.
- The Kolbe–Schmidt reaction provides a pathway to the salicylic acid precursor, aspirin.
laboratory methods
Initial methods for small-scale reactions for research or for the production of finer chemicals often employ expensive consumable reagents.
- Oxidation of primary alcohols or aldehydes with strong oxidants such as potassium dichromate, Jones reagent, potassium permanganate, or sodium chlorite. This method is more suitable for laboratory conditions than industrial use of air, which is “greener” because it produces fewer inorganic side products such as chromium or manganese oxides. [ citation needed ]
- Oxidative cleavage of olefins by ozonolysis, potassium permanganate, or potassium dichromate.
- Hydrolysis of nitriles, esters, or amides, usually with acid- or base-catalysis.
- Grignard reagent and carbonation of organolithium reagents:
RLi + CO 2 → RCO 2 LiRCO 2 Li + HCl → RCO 2 H + LiCl
- Halogenation of haloform reaction in methyl ketone followed by hydrolysis
- Base-catalyzed cleavage of non-enolizable ketones, especially aryl ketones: [6]
RC(O)Ar + H 2 O → RCO 2 H + ArH
less common reactions
Many reactions produce carboxylic acids but are used only in specific cases or are primarily of academic interest.
- Disproportionation of an aldehyde in the Cannizzaro reaction
- The diketone rearrangement in the benzylic acid rearrangement involving the generation of benzoic acid is the von Richter reaction from nitrobenzene and the Kolbe–Schmidt reaction from phenol.
reactions
The most widely practiced reactions convert carboxylic acids into esters, amides, carboxylate salts, acid chlorides, and alcohols. Carboxylic acids react with bases to form carboxylate salts, in which the hydrogen of the hydroxyl (-OH) group is replaced by a metal cation. For example, the acetic acid found in vinegar reacts with sodium bicarbonate (baking soda) to form sodium acetate, carbon dioxide, and water:
CH 3 COOH + NaHCO 3 → CH 3 CoO – Na + + CO 2 + H 2 O
Carboxylic acid also reacts with alcohol to give esters. This process is widely used, for example in the production of polyesters. Similarly, carboxylic acids are converted to amides, but this conversion usually does not occur by a direct reaction of the carboxylic acid and amine. Instead esters are specific precursors of amides. The conversion of amino acids into peptides is an important biochemical process that requires ATP.
The hydroxyl group on the carboxylic acid can be replaced with a chlorine atom using thionyl chloride to give acyl chloride. In nature, carboxylic acids are converted into thioesters.
Less
Like esters, most of the carboxylic acids can be reduced to alcohols by hydrogenation or using hydrides or alkyl transfer agents (because they will deprotonate instead of acids [ more details needed ] without transfer such as) lithium aluminum hydride or Grignard reagents ( organolithium compounds).
N , N -dimethyl (chloromethylene) ammonium chloride (ClHC = N + (CH 3 ) 2 Cl – ) is a highly chemotherapeutic agent for the reduction of carboxylic acids. It selectively activates the carboxylic acid to give the carboxymethyleneammonium salt, which can be reduced by a mild reductant such as lithium tris( t -butoxy) aluminum hydride to afford the aldehyde in a one-pot process. This process is known to tolerate reactive carbonyl functionalities such as ketones as well as moderately reactive esters, olefins, nitriles and halide moieties.
specific reactions
- Like all carbonyl compounds, keto-enols are protonally labeled on the α-carbon due to tautomerization. Thus, the α-carbon is readily halogenated into the Hell–Volhard–Zelinsky halogens.
- The Schmidt reaction converts carboxylic acids to amines.
- Carboxylic acids are decarboxylated in the Hunsdicker reaction.
- The Dakin West reaction converts an amino acid to the corresponding amino ketone.
- In the Barbier–Wieland fallacy, a carboxylic acid methylene bridge on an aliphatic chain having a simpler chain can be shorter than a carbon at the alpha position. The reverse process is the Arndt–Eistert synthesis, where an acid is converted to an acyl halide, which is then reacted with diazomethane to give an additional methylene in the aliphatic chain.
- Many acids undergo oxidative decarboxylation. The enzymes that catalyze these reactions are known as carboxylase (EC 6.4.1) and decarboxylase (EC 4.1.1).
- Carboxylic acids are reduced to aldehydes via esters and DiBl, via acid chlorides in the Rosenmond reduction and via thioesters in the Fukuyama reduction.
- In ketonic decarboxylation carboxylic acids are converted to ketones.
- Organolithium reagents (>2 equiv) react with carboxylic acids to give a dilithium 1,1-diolate, a stable tetrahedral intermediate that decomposes to give a ketone upon acidic workup.
- Kolbe electrolysis is an electrolyte, decarboxylative dimerization reaction. This gets rid of the carboxyl groups of the two acid molecules, and binds the remaining fragments together.
carboxyl radical
The carboxyl radical, •COOH, is present only briefly. [8] The acid dissociation constant of • COOH has been measured using electron paramagnetic resonance spectroscopy. The carboxyl group dimers to form oxalic acid.
frequently Asked question For Carboxyl Group
What is the formula of carbolic acid?
Carboxylic acids have the general formula R-C(O)OH where R represents the remainder of the molecule. Amino acids and acetic acid are carboxylic acids.
Contains amount of carboxylic acid?
Carboxylic acids are hydrocarbon derivatives containing a carboxyl (COOH) moiety. Remember that carbon has four valence electrons and therefore needs four electrons or bonds to complete its octet.
How do you identify carboxylic acids?
Prepare a saturated solution of sodium bicarbonate by dissolving sodium bicarbonate in 1 ml of water. Add the given organic compound to a saturated solution of sodium bicarbonate solution. Stir the solution well. If strong effervescence develops, it indicates the presence of carboxylic acid.
What are carboxylic acid reactions?
The most widely practiced reactions convert carboxylic acids into esters, amides, carboxylate salts, acid chlorides, and alcohols. Carboxylic acids react with bases to form carboxylate salts, in which the hydrogen of the hydroxyl (-OH) group is replaced by a metal cation.
Which is the carboxylic acid group?
-COOH is a carboxylic acid group. Hence, option (B) from the above option will be correct.
Why is carboxylic acid called a weak acid?
Boric acid itself does not give protons. It completes its octet by accepting the hydroxyl ion(OH^(-)) from the water molecule andH^(+)Expels. Therefore, boric acid is a weak acid.
How can you differentiate between alcohol and carbolic acid by experiment?
No gas is produced when a little sodium bicarbonate (NaHCO3) is added to alcohol. When sodium bicarbonate (NaHCO3) is added to a carboxylic acid, carbon dioxide (CO2) gas is produced with effervescence. Hope this answer will help you.
What is another name for organic acid?
organic acids
Organic acids are those organic compounds that have acidic properties. Of these, carboxylic acids are the most common. Sulfonic acid, alcohol etc. are other organic acids. Organic acids are often found in fruit juices.
Which acid is H2co3 ?
Organic acids are organic compounds with the chemical formula H2CO3.
What is an organic ion?
Organic compounds are compounds made up of carbon, hydrogen and other elements. There are often covalent bonds between them and they are soluble in organic solutions only. Examples of these are methane, chloroform, acetic acid, carbohydrate, urea, etc. Their presence is more in organic matter.
How is organic acid formed?
Carbon Dioxide Carbon dioxide is made up of two atoms of oxygen and one atom of carbon. It remains in gaseous state at normal temperature and pressure. This gas is found in the atmosphere up to 0.03% to 0.04%, but its concentration in the air also changes slightly with the change in season.
What is organic and inorganic compound?
Organic Compounds: Organic compounds are compounds that essentially contain carbon atoms in structure along with atoms such as hydrogen, nitrogen, and oxygen. Inorganic Compounds: Inorganic compounds are compounds that do not essentially contain carbon atoms in their structure.
What is the main source of organic compound?
Carbohydrates, amino acids, proteins, RNA and DNA are the main sources of organic compounds.
Why are there more number of organic compounds than organic compounds?
A large number of carbon atoms are held together by covalent bonds. This is the reason why there are many compounds of carbon. Methane, ethane, propane, butane, pentane etc. are compounds of carbon and they are used in many chemical industries.
Why do carbon atoms form a large number of compounds?
Due to tetravalency and catenation property, carbon forms a large number of compounds. Cationation – also shows the property of carbon self-linking in that it forms long branched or cyclic chains to form a large number of compounds. Carbon forms covalent compounds because of the number of electrons present in the last shell.
