Chemistry Grade 11 Notes (Carboxylic Acids) PDF

**[Carboxylic acid]** **Carboxylic acid**, any of a class of [organic compounds](https://www.britannica.com/science/organic-compound) in which a [carbon](https://www.britannica.com/science/carbon-chemical-element) (C) atom is bonded to an [oxygen](https://www.britannica.com/science/oxygen) (O) atom...

**[Carboxylic acid]** **Carboxylic acid**, any of a class of [organic compounds](https://www.britannica.com/science/organic-compound) in which a [carbon](https://www.britannica.com/science/carbon-chemical-element) (C) atom is bonded to an [oxygen](https://www.britannica.com/science/oxygen) (O) atom by a double bond(carbonyl functional group) and to a [hydroxyl group](https://www.britannica.com/science/hydroxyl-group) (―OH) by a single bond. - A fourth bond links the carbon atom to a [hydrogen](https://www.britannica.com/science/hydrogen) (H) atom or to some other univalent combining group. - The carboxyl (COOH) group is so-named because of the *carb*onyl group (C=O) and hydr*oxyl* group. It is usually written as ---COOH or ---CO~2~ H. - The chief chemical characteristic of the carboxylic acids is their acidity. They are generally more acidic than other organic [compounds](https://www.merriam-webster.com/dictionary/compounds) containing hydroxyl groups but are generally weaker than the familiar mineral acids. (e.g., [hydrochloric acid](https://www.britannica.com/science/hydrochloric-acid), HCl, [sulfuric acid](https://www.britannica.com/science/sulfuric-acid), H~2~SO~4~, etc.) because they only partially ionize in solution. Their solutions do not contain many hydrogen ions compared to a solution of a strong acid at the same concentration. 1. **[Saturated monocarboxylic acids]** - The general formula for saturated monocarboxylic acids can be written as: - used in the manufacture of detergents, disinfectants, herbicides, antiseptics, drugs, dyes, explosives, and perfumes - The structure of the first three saturated monocarboxylic acids are written as follows: 2. **[Di- and tricarboxylic acids]** - Carboxylic acids containing two carboxyl groups in their structure are called dicarboxylic acids. - The structure of the first three saturated dicarboxylic acids are shown below: a\. HOOC-COOH Ethanedioic acid b\. HOOC-CH~2~-COOH Propanedioic acid c\. HOOC-CH~2~-CH~2~-COOH Butanedioic acid - involved in important biological processes as donor ligands. Similarly, - carboxylic acids that contain three carboxyl groups in their structure are called tricarboxylic acids. Example: citric acid is a typical tricarboxylic acid. The molecular formula of citric acid is C₆H₈O₇. It is a colourless, odourless, and tasteless crystalline compound. The structure of citric acid crystals download.jpg [Nomenclature](https://www.britannica.com/science/nomenclature)[ of carboxylic acids ] -------------------------------------------------------------------------------------------------- - Common names carboxylic acids - IUPAC names of carboxylic acids 1. **[Straight chain monocarboxylic acids]** - The common names of some basic carboxylic acids are derived from Latin names that indicate the first original natural source of the carboxylic acid. [Structure of Acid ] [Natural Source] [Common Name] ---------------------------------- ------------------------------ --------------------------- HCOOH Ants (Formica) Formic acid CH3 COOH Vinegar (Acetum) Acetic acid CH3 CH2 COOH Basic Fat (Propio) Propionic acid CH3 CH2 CH2 COOH Rancid butter (Butyrum) Butyric acid CH3 CH2 CH2 CH2 COOH Present in a Valerian herb Valeric acid CH3 CH2 CH2 CH2 CH2 COOH Goat (Caper) Caproic acid - In IPUAC system, monocarboxylic acids are named by replacing the terminal "−e" of the corresponding alkane name with "−oic acid." They are named as alkanoic acids. Eg:- 2. **[Branched chain and substituted carboxylic acids]** - In common naming system, the branched chain and substituted acids are named as derivatives of straight chain carboxylic acids. - In this case, the position of the side chain or substituent's is indicated by Greek letters, α, β, γ, δ\... for designating the 1st, 2nd, 3rd,... position of carbon atoms as shown below: δ γ β α Eg:- Cl CH~3~-CH-CH~2~-COOH β-Chlorobutanoic acid - The IUPAC name of a branched carboxylic acid is derived from that of the longest carbon chain that contains the carboxyl group. - The positions of the substitutes are indicated by Arabic numerals as 1, 2, 3. The numbering of the chain starts from the carboxyl carbon and it is always assigned C-1 position. Eg:- CH~3~ --CH(CH~3~ )CH~2~ --COOH 3-methylbutanoic acid 3. **[Dicarboxylic acids]** - Dicarboxylic acids also possess common names which are based on their sources. **[Structure ]** **[Common Name]** **[IUPAC Name]** ------------------------------ ------------------------------- ------------------------------ HOOC−COOH Oxalic acid Ethanedioic acid HOOC−CH~2~ -- COOH Malonic acid Propanedioic acid - In the IUPAC system, dicarboxylic acids are named as alkanedioic acids. These names are obtained by replacing the suffix ''--e'' in the name of corresponding alkane by ''--dioic acid''. 4. **[Aromatic carboxylic acids]** - Aromatic carboxylic acids are compounds which have a carboxyl group directly attached to an aromatic ring. The common name of the simplest aromatic carboxylic acid is benzoic acid. - As an acid, benzoic acid is slightly stronger than acetic acid but, similar to other aromatic compounds, also undergo electrophilic substitution reactions.( an electrophile replaces the \'functional group\' of the molecule. Electrophiles are electron-deficient species that are attracted to an electron-rich center.) Benzoic acid - In common naming system, the position of the substituent is indicated by the prefixes ortho (o-), meta (m-), para (p-) as it is shown in the structure below.  o,p-dimehylbenzoic acid - IUPAC name of the simplest aromatic carboxylic acid is benzenecarboxylic acids. COOH Benzenecarboxylic acid Substituted aromatic acids with one carboxyl group are named as derivatives of benzenecarboxylic acids. - The position of substituents is indicated using the Arabic numerals 1,2,3, etc according to their position on the benzene ring relative to the carboxyl group. The carbon on which the carboxyl group is attached is by convention C-1. **Eg:-** oooo.jpg 2-bromobenzenecarboxylic acid ====================================== [Physical Properties of carboxylic acids] ===================================================== [State] =================== - The lower aliphatic acids containing up to 9 carbon atoms are liquids, whereas the higher members are colourless waxy solids. Benzoic acid and most of its derivatives are also colourless solids. ================================================================================================================================================================================================== [Odor] ================== - The odors of the lower aliphatic acids progress from a sharp, irritating odor of methanoic acid and ethanoic acids to the distinctly unpleasant odor of the butanoic, pentanoic and hexanoic acids. =================================================================================================================================================================================================== [Melting and Boiling Points] ======================================== - The melting points and boiling points of carboxylic acids are higher than those of hydrocarbons and oxygen-containing organic compounds of comparable size and shape and indicate strong intermolecular attractive forces. ========================================================================================================================================================================================================================== The Figure gives boiling point comparison of carboxylic acid with alkene, ketone, and alcohol. ============================================================================================== 2-Methyl-1-butene 2-Butanone 2-Butanol Propanoic acid =====================================================  Methyl-1-butene.png  Methyl-1-butene.png ================================================================================================================= bp (1 atm): 31 °C 80 °C 99 °C 141 °C ==================================== - A unique hydrogen-bonding arrangement, shown in Figure, contributes to these attractive forces. The hydroxyl group of one carboxylic acid molecule acts as a proton donor toward the carbonyl oxygen of a second. ================================================================================================================================================================================================================= - In a reciprocal fashion, the hydroxyl proton of the second carboxyl function interacts with the carbonyl oxygen of the first. The result is that the two carboxylic acid molecules are held together by two hydrogen bonds. =========================================================================================================================================================================================================================== Fig === Carboxylic acid dimer =========================================================================== [Solubility] ======================== - In aqueous solution intermolecular association between carboxylic acid molecules is replaced by hydrogen bonding to water. ========================================================================================================================== - The solubility properties of carboxylic acids are similar to those of alcohols. =============================================================================== - Carboxylic acids of four carbon atoms or fewer are miscible with water in all proportions. Figure shows hydrogen bonding between carboxylic acids and water molecules. ====================================================================================================================================================================== cwh.png ======= - Carboxylic acids have high boiling points compared to other substances of comparable molar mass. Boiling points increase with molar mass. ========================================================================================================================================= - Carboxylic acids having one to four carbon atoms are completely miscible with water. Solubility decreases with molar mass. ========================================================================================================================== The carboxylic acids generally are soluble in such organic solvents as ethanol, toluene, and diethyl ether. =========================================================================================================== [Chemical Properties of carboxylic acids] ===================================================== - The carboxylic acids show reactions due to the alkyl or aryl group and the carboxyl group. The carboxyl group is further considered to be made up of a carbonyl and a hydroxyl group. ===================================================================================================================================================================================== - All these groups modify the properties of each other due to their interaction. Some of the common reactions of carboxylic acids are: ==================================================================================================================================== [Reaction as an acid] ================================= - In aqueous solution, the cleavage of O--H bond occurs leading to the formation of carboxylate ion and hydronium ion. Carboxylic acids ionize partially and an equilibrium exists between the ionized and un-ionized forms. ==========================================================================================================================================================================================================================  + H~2~O arrow.png  + H~3~O^+^ ======================================================================================================================================== Carboxylic acid Carboxylate ion Hydronium ion ============================================= - Carboxylic acids are weak acids and dissociates slightly. The following are examples of reactions of carboxylic acids as an acid. ================================================================================================================================= [Reaction with metals:] Carboxylic acids react with active metals such as Na, K, Mg, Ca, etc. to give metal carboxylate salts, RCO2 − M+ , and hydrogen gas. ======================================================================================================================================================================== Carboxylic-acid.svg.png + 2Na  aa.png + H~2~ =========================================================================== Carboxylic acid Sodium carboxylate ================================== - The salts of carboxylic acids are named by writing the name of the metal first, followed by the name of the acid replacing the ending -ic acid by -ate. ======================================================================================================================================================= For example, sodium reacts with ethanoic acid to form sodium ethanoate and hydrogen. ==================================================================================== 2CH~2~-COOH + 2 Na  2CH~3~-COONa + H2 ==================================================================== [Reaction with Bases]: Carboxylic acids react with strong bases like sodium hydroxide or potassium hydroxide to form the corresponding metal carboxylate salts and water. ===================================================================================================================================================================================== Carboxylic-acid.svg.png + NaOH  aa.png + H~2~O ============================================================================= Carboxylic acid Sodium carboxylate ================================== - Reaction with a base is a simple neutralization reaction. Carboxylic acids react with weak bases like carbonates or bicarbonates to form salt, water and carbon dioxide. + Na~2~CO~3~ arrrev.png  + H~2~O + CO~2~ ========================================================================================================================================================================================================================================================================================= Carboxylic-acid.svg.png + NaHCO~3~  aa.png + H~2~O + CO~2~ ========================================================================================== They also react with ammonia to form ammonium salts of carboxylic acids. ========================================================================  + NH~3~ arrrev.png  ============================================================================================= Ammonium carboxylate ==================== [Formation of Esters:] ================================== - One of the important reactions of carboxylic acids involves the replacement of --OH group by an alkoxy group to form esters as products. In this reaction, carboxylic acids are heated with alcohols in the presence of concentrated sulphuric acid. The reaction is called [esterification]. ========================================================================================================================================================================================================================================================================================================= Carboxylic-acid.svg.png + H-O-R  R-C-O-R' + H~2~O ================================================================================= Carboxylic acid Alcohol Ester ============================= [Synthesis(preparation) of carboxylic acids] ======================================================== [Hydrolysis](https://www.britannica.com/science/hydrolysis)[ of acid derivatives] --------------------------------------------------------------------------------------------- - All acid derivatives can be hydrolyzed (cleaved by [water](https://www.britannica.com/science/water)) to yield carboxylic acids; the conditions required range from mild to severe, depending on the [compound](https://www.merriam-webster.com/dictionary/compound) involved. ============================================================================================================================================================================================================================================================================== - The easiest acid derivatives to hydrolyze are [acyl chlorides](https://www.britannica.com/science/acyl-chloride), which require only the addition of water. =========================================================================================================================================================== RCOCL + H~2~O arrow.png RCOOH ============================= - Carboxylic acid salts are converted to the corresponding acids instantaneously at room temperature simply on treatment with water and a strong acid such as [hydrochloric acid](https://www.britannica.com/science/hydrochloric-acid). ====================================================================================================================================================================================================================================== RCOO^-^ + H2O  RCOOH =================================================== [Oxidation] ======================= - One of the important methods for preparation of carboxylic acids is oxidation. Many saturated monocarboxylic acids are obtained by the oxidation of the corresponding primary alcohols, whereas aromatic acids are obtained from the corresponding alkylbenzenes. ================================================================================================================================================================================================================================================================= [Oxidation of Primary Alcohols] =========================================== The primary alcohols are readily oxidized to the corresponding carboxylic acids by their reaction with common oxidizing agents like K2 Cr2 O7 or KMnO4. ======================================================================================================================================================== R-CH~2~-OHarrow.png =============================================================== 1° Alcohol ========== For example, oxidation of ethanol yields acetic acid (ethanoic acid). ===================================================================== CH~3~-CH~2~-OH arrow.png CH~2~-C-OH =================================== [Oxidation of Alkylbenzenes] ======================================== Aromatic compounds containing alkyl group as substituent undergo oxidation to form aromatic acids. ================================================================================================== The reaction involves oxidation with KMnO4 or K2 CrO7 under vigorous conditions. The alkyl group is oxidized to carboxyl group irrespective of its size. ======================================================================================================================================================== For example, toluene and ethylbenzene, both give benzoic acid on refluxing with KMnO4 in alkaline medium. =========================================================================================================  arrow.png ================================================================= Toluene Benzoic acid ==================== [Preparation of acetic acid (Ethanoic acid)] ======================================================== - Acetic acid is one of the important carboxylic acids which is used as food preservative. ======================================================================================== - It can be prepared in laboratory by the oxidation of ethanol with potassium permanganate. ========================================================================================= - It can also be obtained by passing the vapours of ethanol through copper oxide. =============================================================================== - Large quantities of acetic acid are obtained in industry from fermentation of ethanol. The process is known as Quick Vinegar Fermentation Process. ================================================================================================================================================== - In the process large wooden vats fig are used which have a perforated bottom. They are packed with wood shavings moistened with old vinegar. ============================================================================================================================================ - Ethanol solution is poured from the top and trickles down slowly to the perforated bottom. From the lower portion, air is pumped in the vat. The bacteria present in old vinegar, ferment the ethanol into acetic acid. ======================================================================================================================================================================================================================= - The liquor obtained at the bottom is recirculated through the tower. The maximum concentration of acetic acid obtained by this process is about 10%, which can be fractionated to yield glacial acetic acid (anhydrous acetic acid). ==================================================================================================================================================================================================================================== Fatty acids are carboxylic acids with long hydrocarbon chains. The fatty acids most frequently found in nature are shown in Table. =================================================================================================================================== +-----------------------+-----------------------+-----------------------+ | [Number of carbons ]{ | [Common Name]{.underl | [Structure / Formula] | |.underline} | ine} | | | ===================== | ===================== | ===================== | | =========== | ==== | ============ | +=======================+=======================+=======================+ | ­ [Saturated]{.underl | | | | ine} | | | | ===================== | | | | ==== | | | +-----------------------+-----------------------+-----------------------+ | 12 | Lauric acid | CH~3~ (CH~2~ )~10~COO | | == | =========== | H | | | | ===================== | | | | = | +-----------------------+-----------------------+-----------------------+ | U[nsaturated.]{.under | | | | line} | | | | ===================== | | | | ===== | | | +-----------------------+-----------------------+-----------------------+ | 18 | Oleic acid | CH~3~ (CH~2~ )~7~ CH= | | == | ========== | CH(CH~2~)~7~ COOH | | | | ===================== | | | | ================= | +-----------------------+-----------------------+-----------------------+ Most naturally occurring fatty acids contain an even number of carbon atoms and are unbranched. Fatty acids can be classified as saturated or unsaturated. ========================================================================================================================================================== - saturated compounds have only one carbon bond, whereas unsaturated compounds consist of double and triple carbon bonds. Double bonds in naturally occurring unsaturated fatty acids are never conjugated. ========================================================================================================================================================================================================= - The physical properties of a fatty acid depend on the length of the hydrocarbon chain and the degree of unsaturation. The melting points of saturated fatty acids increase with increasing molecular weight because of increased van der Waals interactions between the molecules. ================================================================================================================================================================================================================================================================================== - The intermolecular interactions of unsaturated molecules are much weaker than saturated molecules. As a result, the melting points are much lower for unsaturated fatty acids. ============================================================================================================================================================================== - The melting points of the unsaturated fatty acids decrease as the number of double bonds increases. For example, an 18-carbon fatty acid melts at 69 °C if it is saturated, at 13 °C if it has one double bond, at -5 °C if it has two double bonds, and at -11 °C if it has three double bonds. ================================================================================================================================================================================================================================================================================================ [Uses of carboxylic acid] ===================================== - Acetic acid is used as a solvent and as a starting material in the preparation of acetates, acetic anhydride, etc. ================================================================================================================== - It is also used to prepare the vinyl acetate polymer which is used in paints and adhesives. =========================================================================================== - Vinegar contains about 8-10% acetic acid which is used in many food items. ========================================================================== - Perhaps one of the most important industrial applications of long chain carboxylic acid is for making soaps, detergents, and shampoos. ====================================================================================================================================== - Carboxylic acids occur widely in nature. The [fatty acids](https://www.britannica.com/science/fatty-acid) are components of glycerides, which in turn are components of [fat](https://www.britannica.com/topic/fat). - Hydroxyl acids, such as [lactic acid](https://www.britannica.com/science/lactic-acid) (found in sour-milk products) and [citric acid](https://www.britannica.com/science/citric-acid) (found in citrus fruits), and many keto acids are important metabolic products that exist in most living [cells](https://www.britannica.com/science/cell-biology). -  [Proteins](https://www.britannica.com/science/protein) are made up of [amino acids](https://www.britannica.com/science/amino-acid), which also contain carboxyl groups. Compounds in which the ―OH of the carboxyl group is replaced by certain other groups are called [carboxylic acid derivatives](https://www.britannica.com/science/carboxylic-acid-derivative), the most important of which are acyl halides, acid anhydrides, acid chloride, [esters](https://www.britannica.com/science/ester-chemical-compound), and [amides](https://www.britannica.com/science/amide). **[Anhydrides:]** The acid anhydride functional group results when two carboxylic acids combine and lose water (anhydride = without water). **Structure** \- acid-anhydride.png **Naming** - acid anhydrides are named like carboxylic acids except the ending -acid is replaced with --anhydride. This is true for both the IUPAC and Common nomenclature. **Physical properties** Let us take ethanoic anhydride as typical **Appearance** Ethanoic anhydride is a liquid with no colour and smells strongly of vinegar (ethanoic acid). **Solubility in Water** Ethanoic anhydride cannot be said to dissolve in water because it reacts with it to form ethanoic acid. **Boiling Point** Ethanoic anhydride\'s boiling point is at 140°C. This is only because it is fairly a big polar molecule, and so has both dipole-dipole attractions and van der Waals dispersion forces However, it doesn\'t form hydrogen bonds. It means that the boiling point is not as high as that of a carboxylic acid of a similar size. For example, pentanoic acid (one of the most similarly sized acids) boiling point is at 186°C. **[Amide:-]** is usually an organic compound that contains a functional group consisting of an acyl group (R--C=O) linked to a nitrogen atom: The simplest amides are derivatives of ammonia (NH~3~) in which one hydrogen atom has been replaced by an acyl group. **Structure**  **Naming** - In names for amides, the -ic acid of the common name or the -oic ending of the IUPAC for the corresponding carboxylic acid is replaced by -amide. **Physical properties** - Like the esters, solutions of amides in water usually are neutral---neither acidic nor basic. - The amides generally have high boiling points and melting points. These characteristics and their solubility in water result from the polar nature of the amide group and hydrogen bonding  **[Acid chloride:-]** has the molecular formula RCOCl, where R is a side chain. They are carboxylic acid reactive derivatives. - An acyl chloride (or acid chloride) is an organic compound composed of a chlorine atom attached to an acyl group in organic chemistry. **Structure** acyl-chloride.png **Naming** - Acyl chlorides are named by taking the name of the parent carboxylic acid and substituting -yl chloride for -ic acid where the acyl chloride substituent takes priority. **Physical properties** Appearance- Lower acyl chlorides are colourless liquids with a strong odour. Solubility- They dissolve in organic solvents like alcohol, ether, and chloroform. Lacking the ability to form hydrogen bonds, acyl chlorides have lower boiling and melting points than similar carboxylic acids. **Carboxylic acid [derivatives](https://www.britannica.com/dictionary/derivatives) have varied applications.** For example - In addition to its use as a disinfectant, [formic acid](https://www.britannica.com/science/formic-acid), the simplest carboxylic acid, is employed in [textile](https://www.britannica.com/topic/textile) treatment and as an acid reducing agent. -  [Acetic acid](https://www.britannica.com/science/acetic-acid) is extensively used in the production of cellulose [plastics](https://www.britannica.com/science/plastic) and esters. [Aspirin](https://www.britannica.com/science/aspirin), the [ester](https://www.britannica.com/science/ester-chemical-compound) of [salicylic acid](https://www.britannica.com/science/salicylic-acid), is prepared from acetic acid. - Palmitic acid and [stearic acid](https://www.britannica.com/science/stearic-acid) are important in the manufacture of soaps, cosmetics, pharmaceuticals, candles, and protective coatings. - Stearic acid also is used in [rubber](https://www.britannica.com/science/rubber-chemical-compound) manufacture. - Acrylic acid is employed as an ester in the production of [polymers](https://www.britannica.com/science/polymer) (long-chain molecules) known as acrylates. - Methacrylic acid serves as an ester and is polymerized to form [Lucite](https://www.britannica.com/science/Lucite). - Oleic acid is used in the manufacture of soaps and detergents and of textiles. ***[Experiment 6.3]*** **[Laboratory Preparation of Acetic Acid]** **Objective :Observation and analysis** 1\. *What happened to the color of the solution in the flask?* *2. What is the role of sodium dichromate in the above reaction? Is it oxidized or reduced?* *3. Write the chemical equation for this reaction.* *4. What do you conclude from this experiment?* **[Answer]** **1,** The color of the solution in the flask likely changed during the reaction. Sodium dichromate is usually orange or reddish-orange in color, and upon oxidation, it may change to a green color. **2,** Sodium dichromate serves as an oxidizing agent in this reaction. It oxidizes ethanol to ethanoic acid (acetic acid). In the process, sodium dichromate itself is reduced. **3,** The chemical equation for the oxidation of ethanol to ethanoic acid using sodium dichromate as the oxidizing agent can be represented as: CH3CH2OH + Na2Cr2O7 + H2SO4 → CH3COOH + Na2SO4 +Cr2(SO4OH)2 + H2OCH3​CH2​OH + Na2​Cr2​O7​+H2​SO4 ​→ CH3​COOH + Na2​SO4 ​+ Cr2​(SO4​OH)2​ + H2​O 4, Rom this experiment, we can conclude that ethanol can be oxidized to form acetic acid (ethanoic acid) in the laboratory setting. The reaction is facilitated by the presence of sodium dichromate as an oxidizing agent and sulfuric acid as a catalyst. The change in color, odor, and pH of the product confirms the formation of acetic acid. **[SOURCE]** - **[CHEMISTRY TEXT BOOK]** - [**https://www.vedantu.com**](https://www.vedantu.com) - **[https://www.britannica.com/]** - [**https://chem.libretexts.org**](https://chem.libretexts.org) - **[https://www.sciencedirect.com/]** **[\ \ \ ]**