Carboxylic Acid and its Deriva4ves Carboxylic Acids & Deriva4ves •  Compounds characterized by the presence of a carboxyl group (-‐COOH) (carbonyl + hydroxyl = carboxyl) •  They are weak acids and they par4ally dissociate in water to release protons •  Deriva4ves of carboxylic acids are derived by replacing the hydroxyl group by alkoxyl, chlorides, amines and another carboxylic acid •  The unchanged group is called acyl group hGp://chemwiki.ucdavis.edu/@api/deki/ﬁles/2726/image007.png?revision=1 Carboxyl group Physical Proper4es of Carboxylic Acids •  Carboxylic acids (CAs) are composed of two very polar func4onal groups, the carbonyl group and the hydroxyl group •  CAs can make hydrogen bonding within themselves and with water molecules •  CAs have higher boiling points then aldehydes, ketones and alcohols of similar molecular weight •  Small CAs are soluble in water, solubility decreases as the carbon content increases (for example; hexadecanoic acid is insoluble in water) •  Longer-‐chain CAs are classiﬁed as faGy acids and they are important components of biological membranes and triglycerides (major storage form of lipid in the body) hGp://ﬁgures.boundless.com/29510/full/Screenshot%202014-‐08-‐25%2000.18.01.png Naming Carboxylic Acids: IUPAC system 1) Determine the name of the parent compound (longest carbon chain aGached to the carboxyl group) 2) Carboxyl carbon is always “carbon number 1”, the other carbons are numbered accordingly 3) Replace the –e ending of parent alkane with –oic acid (for two carboxyls, -‐dioic acid) 4) Name and number subs4tuents in the usual way hGp://chemwiki.ucdavis.edu/@api/deki/ﬁles/12845/2.jpg?size=besfit&width=351&height=272&revision=1 Benzoic acid Important Carboxylic Acids •  Formic (methanoic) acid: found in ant •  Ace4c (ethanoic) acid: in vinegars •  Propionic (propanoic) acid: product of bacterial fermenta4on of milk products Formic acid Ace4c acid •  FaGy acids – long-‐chain monocarboxylic acids, found in palm oil, buGer, coconut oil, milk, animal fat – faGy acids are major energy storage molecules in the form of triglycerides •  Aroma4c carboxylic acid: benzoic acid (preserva4ve in food), salicylic acid (disinfectant), acetylsalycilic acid (aspirin) aspirin Reac4ons of Carboxylic Acids 1) Prepara4on of Carboxylic Acids 2) Acid-‐base Reac4ons: 3) Esteriﬁca4on: 1) Prepara4on of Carboxylic Acids •  Mainly obtained by oxida4on of alcohol or aldehydes by an oxidizing agent (e.g. KMnO4, chromic acid) hGp://www.cliﬀsnotes.com/assets/23083.jpg 2) Acid-‐Base Reac4ons: •  Carboxylic acids are weak acids that dissociate par4ally to form a carboxylate ion and a hydrogen ion (proton) •  They are weak acids because they dissociate par4ally in solu4on (mostly less then 5 % of the acid is ionized-‐dependent on pKa) •  Carboxylic acids react with strong bases (sodium hydroxide) to form water and the salt of the carboxylate ion (neutraliza4on reac4on) •  The salt of the carboxylate ion is named by replacing –ic acid suﬃx by –ate, e.g. sodium acetate •  Carboxylic acid salts are ionic molecules and are very soluble in water (long-‐chain carboxylic acid salts are called soaps) hGp://science.uvu.edu/ochem/wp-‐content/images/C/carboxylicacidsalt1.png 3) Esteriﬁca4on •  Carboxylic acids react with alcohols to form esters and water (condensa4on/dehydra4on reac4on) hGp://chemistry.tutorvista.com/organic-‐chemistry/esteriﬁca4on.html Esters •  Physical Proper4es: •  Esters are formed by the reac4on of carboxylic acids with alcohols Condensa4on reac4on •  Esters have intermediate polarity (less polar than carboxylic acids) •  Esters have pleasant aromas and many esters are found naturally in food; banana oil, pineapples, raspberries •  Esters have similar boiling points as aldehydes and ketones (no hydrogen bonding between their molecules) •  Small esters are soluble in water hGp://www.materialsworldmodules.org/resources/polimariza4on/4-‐condensa4on.html hGp://ﬁgures.boundless.com/29510/full/Screenshot%202014-‐08-‐25%2000.18.01.png Naming Esters •  Both the name of the carboxylic acid and the alcohol are reﬂected in the name of the ester •  1) The name of the alkyl or aryl por(on of the alcohol becomes the ﬁrst word •  2) The name of the carboxylic acid becomes the second word; a modiﬁca;on of “–ic acid” to “–ate” is made at the end of the carboxylic acid name Name of carboxylic acid Replace “–ic” acid with “-‐ate” Name of the alkyl por4on of alcohol Prepara4on of Esters (Esteriﬁca4on) •  Esters are prepared by reac4on of a carboxylic acid with an alcohol in the presence of small amount of acid and heat Δ hGp://2012books.lardbucket.org/books/introduc4on-‐to-‐chemistry-‐general-‐organic-‐and-‐biological/sec4on_18/0349eb85db710b927a53b2862148f4d7.jpg Hydrolysis of Esters •  Hydrolysis is cleavage of any bond by the addi4on of water molecule •  Esters undergo hydrolysis reac4on in water to generate alcohol and carboxylic acid •  This is the reverse reac4on of esteriﬁca4on •  Hydrolysis is slow at neutral pH •  Small amount of acid/base and heat makes this reac4on much faster H+ or -‐OH Δ Saponiﬁca4on •  Base-‐catalyzed hydrolysis of an ester is called saponiﬁca4on •  The resul4ng carboxylic acid exists as ca4onic salt (R’ – long chain alkyl group) Triglyceride (faGy acid ester) glycerol soap •  Soaps are produced by the reac4on of natural fats and oils (triesters of glycerols) with a strong base •  The polar carboxylate end of soap is hydrophilic and dissolves easily in waterThe nonpolar hydrocarbon chain of sopa is hydrophobic and dissolves nonpolar compounds – this is how soap cleans oil and grease hGp://cornellbiochem.wikispaces.com/ﬁle/view/saponiﬁca4on.gif/408890758/saponiﬁca4on.gif Some Esters found in food hGp://chemwiki.ucdavis.edu/Organic_Chemistry/Organic_Chemistry_With_a_Biological_Emphasis/Chapter_12%3A_Acyl_subs4tu4on_reac4ons/Sec4on_12.4%3A_Esters Acid Chlorides •  Carboxylic acid deriva4ve; hydroxyl is replaced by chloride •  Naming: “-‐ic acid” of the carboxylic acid parent name is replaced by “-‐oyl chloride” •  Proper;es: •  1) Noxious (harmful, unpleasant), irrita4ng chemicals – must be handled with great care •  2) Slightly polar and boil at similar temperatures to the corresponding aldehydes and ketones •  3) React violently with water •  Acid chlorides are the most reac;ve among all carboxylic acid deriva;ves (used for syhthesis of esters and amides) hGp://chemwiki.ucdavis.edu/Organic_Chemistry/Acid_Halides/Nomenclature_of_Acid_Halides Prepara4on and Reac4ons of Acid Chlorides •  Prepara;on: Prepared from carboxylic acids by reac4ng with PCl3, PCl5 or SOCl2 •  Hydrolysis of acid chlorides: Violent reac4on – carboxylic acid and HCl are formed •  Reac;ons with alcohols: an easy way of producing esters hGp://archives.library.illinois.edu/erec/University%20Archives/1505050/Organic/Acids/Chapter%2011/sec11-‐8/ﬁg11-‐19.gif hGp://www.chemguide.co.uk/organicprops/acylchlorides/oxygen.html Acid Anhydrides •  Acid anhydrides are carboxylic acid deriva4ves; hydroxyl group is replaced by a carboxyl group •  Made up of two carboxylic acid molecules minus a water molecule •  Naming: If symmetrical – alkan + oic + “anhydride” (instead of “carboxylic acid”) •  If unsymmetrical, arrange the name of the parent carboxylic acids according to alphabe4cal order or from smaller to larger anhydride means without water) hGp://www.chemguide.co.uk/organicprops/anhydrides/background.html#top hGp://chemwiki.ucdavis.edu/Organic_Chemistry/Anhydrides/Nomenclature_of_Anhydrides Prepara4on and Reac4ons of Acid Anhydrides •  Prepara;on: Typically prepared from the reac4on of acid chlorides with carboxylic acid Base catalyst •  Hydrolysis: Acid anhydrides easily undergo hydrolysis reac4on with water •  Reac;on with alcohols: Acid anhydrides react with alcohols to generate ester and carboxylic acid hGp://chemwiki.ucdavis.edu/Organic_Chemistry/Anhydrides/Reac4ons_of_Anhydrides Phosphoesters and Thioesters Phosphoesters Thioesters phosphoester •  Acetyl-‐CoA carries the acetyl group from glycolysis or beta-‐oxida;on of a faCy acid to an intermediate of the citric acid cycle •  Energy from ATP is made available through hydrolysis of either of the two phosphoanhydride bonds hGps://www.rpi.edu/dept/bcbp/molbiochem/MBWeb/mb1/part2/images/atp.gif hGp://chemwiki.ucdavis.edu/Organic_Chemistry/Organic_Chemistry_With_a_Biological_Emphasis/Chapter_12%3A_Acyl_subs4tu4on_reac4ons/Sec4on_12.3%3A_Thioesters