Esters and water are formed when alcohols react with carboxylic acids. Protonation of the hydroxyl group gives water, which is a superior leaving group (i.e. The reverse reaction is called hydrolysis. The mechanism of intramolecular esterification is the same as the mechanism of the esterification described above. A lone pair of oxygen forms the π bond which will expel water as a good leaving group. Table of Contents Mechanism of Esterification Esterification is a chemical reaction that occurs between the acid (usually carboxylic acid) and the alcohol (or compounds containing the hydroxyl group) where esters are obtained. In the intramolecular reaction, a cyclic ester is formed. The reaction between carboxylic acid and alcohol is known as the Fischer esterification. A reminder of the facts. Save my name, email, and website in this browser for the next time I comment. Step 1: Formation of cation. This type of reaction is called a condensation reaction, which means that water molecules are eliminated during the reaction. Esters are formed when the carboxylic acid is heated with the alcohol in the presence of a catalyst. Subsequent 1,2-elimination of water, in the fourth step, leads to the protonated ester. ChemistryScore is an online resource created for anyone interested in learning chemistry online. And this is one of the most important reactions of carboxylic acids. In the second step, the carbonyl carbon is susceptible to nucleophilic attack by ethanol. The water will not be a viable nucleophile that will reverse the reaction because its concentration will be low compared to the concentration of the methanol. Cheng-zheng Tang, Hong-xiu Tao, Xiao-qing Zhan, and Xin-an Xie* Cornstalk cellulose was liquefied in sub- and supercritical ethanol using an autoclave at 320 °C with 160 mL of ethanol. Unless otherwise noted, LibreTexts content is licensed by CC BY-NC-SA 3.0. Missed the LibreFest? And then, one of the hydroxyl groups takes the proton from protonated alcohol.). Mechanism of Esters Formation during Cellulose Liquefaction in Sub- and Supercritical Ethanol. In the third step, proton transfer from the oxonium ion to one of the OH groups gives us an activated complex. It is also possible to intramolecular esterification if we have a molecule that contains both the carboxylic and hydroxyl groups. Ethanoic acid reacts with ethanol in the presence of concentrated sulphuric acid as a catalyst to produce the ester, ethyl ethanoate. (Depending on the literature, you can find this step divided into two where the alcohol deprotonates the oxonium ion to give tetrahedral intermediate. Most carboxylic acids are suitable for the reaction, but the alcohol should generally be a primary or secondary alkyl. In the last step, deprotonation gives us our final product – ester! In this process, water is also obtained. A salt of the carboxylic acid is formed instead of the acid. The mechanism for the formation of ethyl ethanoate. Cyclic esters are also called lactones. The conditions for esterification are as follow: E.g. I would love to hear what you have to think. This gives us the oxonium ion. The reaction takes place in acidic environments. Is the esterification reaction SN1 or SN2. The π bond of the carbonyl group can act as a base to a strong inorganic acid due to the distortion of the electrons from the electronegativity difference between the oxygen atom and the carbon atom and also the resonance dipole. It, therefore, falls into the category of “condensation reactions“. Esterification is a chemical reaction that occurs between the acid (usually carboxylic acid) and the alcohol (or compounds containing the hydroxyl group) where esters are obtained. It, therefore, falls into the category of “condensation reactions“. For more information contact us at info@libretexts.org or check out our status page at https://status.libretexts.org. Water can also act as nucleophile and revese the reaction is it possible??? However, upon addition of catalytic amounts of an acid, the two components combine in an equilibrium process to give an ester and water. It causes the carbonyl function (makes the carbonyl carbon more electrophilic) to undergo nucleophilic attack by the alcohol; and, 2. Remember that there are many methanol molecules in the solution...it is always in excess in this reaction. In the first step, protonation of the carbonyl oxygen gives a delocalized carbocation (resonance structures aren’t shown in this mechanism because they don’t play an important role) which makes the carbonyl carbon a much better electrophile. The reaction takes place in acidic environments. Watch the recordings here on Youtube! With over 200+ pages of content (and growing), we hope that you dive deep into the realms of chemistry and understand how the structure and composition of matter explain our world. Step 2: The methanol can act as a nucleophile to a carbocation.Remember that there are many methanol molecules in the solution...it is always in excess in this reaction. Have questions or comments? In this reaction, the concentrated sulphuric acid is used as a catalyst, dry form of hydrogen chloride gas is used in some cases. Step 4: The alcohol oxygen atom from the hydroxy group can donate a pair of electrons to the carbon atom making a π bond and eliminating water. Legal. weaker base) in the elimination step. Since esterification is a reversible reaction, esters can undergo hydrolysis to form corresponding alcohol and organic acid. Home | Contact | About | Amazon Disclaimer | Terms and Conditions | Privacy Policy | Legal Disclaimer | Sitemap, 1. A lone pair of oxygen makes a bond with the carbonyl carbon and π bond breaks. Mechanism Of Formation Of Esters From Carboxylic Acids. This reaction is called esterification, which is a reversible reaction. Saponification is an alkaline hydrolysis of esters. This reaction is called esterification, which is a reversible reaction. It can be catalyzed by both acid and base. If you have any questions or would like to share your reviews on the Esterification, then comment down below. Esters and water are formed when alcohols react with carboxylic acids. In this process, water is also obtained. The LibreTexts libraries are Powered by MindTouch® and are supported by the Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot. […] All the steps are reversible; therefore, either addition of excess alcohol or removal of water favors esterification. The cation produced in the reaction with sulfuric acid will have resonance stabilization. A proton can be transferred to one of the hydroxyl groups and thus make it a good leaving group. We also acknowledge previous National Science Foundation support under grant numbers 1246120, 1525057, and 1413739. Step 2: The methanol can act as a nucleophile to a carbocation. This type of reaction is called a condensation reaction, which means that water molecules are eliminated during the reaction. Step 5: The water will be in too low a concentration to reverse the reaction.