Synthesis of benzocaine

We use cookies to give you the best experience possible. The resulting synthesised compound was subject to IR and melting point analyses in order to determine the identity and indeed the purity of the obtained sample. Don't use plagiarized sources. The ester group is essential in body detoxification of this substance due to enzymatic cleavage of the ester linkage.

Other anaesthetics may also contain a tertiary amine functional group which translates into the compound being soluble in the body. Stoichiometric Equations: C. Thus the theoretical yield of benzocaine is expected to be 0.

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Results: Addition of concentrated sulfuric acid to the p-aminobenzoic acid, ethanol mix generated a white solid precipitate to form. Broad peaks due to H-bonding. This effect obviously contributes more heavily than magnetic anisotropy, which in this case would produce the opposite effect; negative shielding would result, moving the signal downfield. Also magnetic anisotropy causes negative shielding again contributing to the downfield move in chemical shift.

Discussion: The reaction mechanism for the synthesis of benzocaine is divided into six key steps: 1 the protonation of the carbonyl by sulfuric acid to give a resonance stabilised intermediate; NH2 is also protonated 2 nucleophillic attack of the alcohol at the carbonyl carbon 3 loss of oxonium leaving group 4 proton transfer leading to a tetrahedral carbonyl addition intermediate 5 further proton transfer leading to a new oxonium ion and its subsequent loss giving 6 the acidified product, water and regeneration of the acid catalyst; finally the product is neutralised with sodium carbonate.

The identity of the synthesised compound was confirmed through IR and melting point analyses to be that of benzocaine. In particular, the obtained IR spectrum iterated the presence of structures such as a 1,4 di-substituted aromatic ring, primary aromatic amine, and an ester functional group directly attached to the aromatic ring as a result of lower frequency of the carbonyl than expected due to conjugation from the aromatic ring.

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Synthesis of Benzocaine Essay. Accessed April 10, This is just a sample. You can get your custom paper from our expert writers. All you need to do is fill out a short form and submit an order. See Pricing. What's Your Topic? Hire a Professional Writer Now. The input space is limited by symbols. What's Your Deadline? How Many Pages? Sign Up and See Pricing.Synthesis of esters has played a significant role in Organic chemistry since its infancy.

The importance lies in the utility of esters both in laboratory field and industry field. In laboratory esters are important sources of corresponding amides.

synthesis of benzocaine

Also esters can be used to product ketones and aldehydes. The essential feature of esterification reaction lies in its broad utilization in industry. Esters ranging from aliphatic to aromatic are generally used as plasticizers, solvents, perfumes, and flavor chemicals and also as precursors for pharmaceuticals, agrochemicals and fine chemicals.

However, Fischer Esterification is not a perfect reaction in the industry field. The use of traditional acidic catalyst such as sulfuric acid will cause side reactions and corrosion of equipment and require removal large amount of salt waste during neutralization of acid. Since esters lack hydrogen-bond donating hydrogenthe intermolecular force between the ester molecules are very week. Many esters have aroma and this property has been used in production of essence. Benzocaine is a white solid which is generally used as a external- used anesthetic.

For example, it can be used to relive pain due to the oral injection. In this experiment, benzocaine will be synthesized by Fischer Esterification of p-aminobenzoic acid with ethanol in an acidic condition. The mechanism of this reaction is involved in several steps.

First, the starting material p-aminobenzoic acid is activated by protonation of carbonyl oxygen. Second, the tetrahedral intermediate is formed by nucleophilic attack of ethanol on the p-aminobenzoic acid. In the third step transfer of a proton from one oxygen atom to another yields a second tetrahedral intermediate and converts the Hydroxyl group into a good leaving group. Finally, the loss of a proton from oxygen and expulsion of water regenerates the acid catalyst and gives the ester product benzocaine.

The purpose of this experiment is to synthesis benzocaine by Fischer Esterification. Refluxing method to the reaction mixture will be used in the experiment in order to proceed the esterification reaction without decreasing the amount of solvent. To precipitate the product from solution, the PH of reaction mixture is made to eight. The product will be isolated by vacuum filtration and washed by distilled water.

Experimental 4-aminobenzoic acid 0. After it cooled to room temperature, 0. The reaction mixture was then refluxed for about 60 to 75 minutes at Upon the completion of reaction, saturated.National Hazard. International Hazard. Department of Redundancy Department - Now with paperwork! Hazard to Self. Hazard to Others. Super Moderator. Not logged in [ Login ]. Back to:. Printable Version. Synthesis of Benzocaine Purpose: To prepare benzocaine a local anesthetic from p-aminobenzoic acid and ethanol, via a Fischer esterification reaction.

Experimental: 1 As with most Fischer esterifications, the alcohol is the excess reagent, and also serves as the solvent for the reaction. It remained thick and milky. This caused the precipitate do dissolve.

This caused the benzocaine to precipitate from the solution, and 2 layers formed, with the bottom one being aqueous. Conclusions: The theoretical yield for this reaction was This corresponds to a Verdict: Not that great The organic layer was found to contain about 5 times more product than the aqueous layer.

This will serve to trap water produced during the reaction. Sorry for lack of pictures. Excellent example of a classic lab, and good notes! I would love to see how the yields compare with your changes for next time. Also, what was the source of the material? I would have used about 1. If you got the idea from that video that I somewhat regret putting up about methyl benzoate, that won't do much to improve yield and will probably reduce it through physical entrainment.

You're already using a large excess of alcohol to drive the equilibrium in favor of product. Personal thoughts: Most of your missing yield is probably unconverted PABA, rinsed away with the alkaline water at the end of the reaction as sodium p-aminobenzoate. Did you do any product characterization? Did you not check for consumption of starting material by TLC or other means?

Synthesis of Benzocaine

How do you know that the reaction was "done" after 2 hr reflux clearly it wasn't but you know what I'm getting at? UnintentionalChaos's comments are all valid, particularly the first two. You're not using enough acid as "catalyst": you're forming substoichiometric amine bisulfate that white solid in suspension This is probably the biggest reason for the low conversion. One further comment: 10g is a pretty big first run.

I would prefer to see a 1 g scale use test to work out the problems, then scale up when everything is satisfactory, otherwise you're burning materials.Benzocainesold under the brand name Orajel amongst others, is an ester local anesthetic commonly used as a topical pain reliever or in cough drops.

It is the active ingredient in many over-the-counter anesthetic ointments such as products for oral ulcers. In the US, products containing benzocaine for oral application are contraindicated in children younger than two years old.

In European countries, the contraindication applies to children under 12 years of age. It was first synthesised in in Germany and approved for medical use in Benzocaine is indicated to treat a variety of pain -related conditions. It may be used for:.

Benzocaine is generally well tolerated and non-toxic when applied topically as recommended. However, there have been reports of serious, life-threatening adverse effects e. Overapplication of oral anesthetics such as benzocaine can increase the risk of pulmonary aspiration by relaxing the gag-reflex and allowing regurgitated stomach contents or oral secretions to enter the airway.

Applying an oral anesthetic and consuming beverages before going to bed can be particularly hazardous. Symptoms of methemoglobinemia usually occur within minutes to hours of applying benzocaine, and can occur upon the first-time use or after additional use.

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Benzocaine may cause allergic reactions. Pain is caused by the stimulation of free nerve endings. When the nerve endings are stimulated, sodium enters the neuroncausing depolarization of the nerve and subsequent initiation of an action potential.

The action potential is propagated down the nerve toward the central nervous systemwhich interprets this as pain.

synthesis of benzocaine

Benzocaine acts to inhibit the voltage-dependent sodium channels VDSCs on the neuron membranestopping the propagation of the action potential. Benzocaine is the ethyl ester of p -aminobenzoic acid PABA. It can be prepared from PABA and ethanol [25] by Fischer esterification or via the reduction of ethyl p -nitrobenzoate. Benzocaine is sparingly soluble in water; it is more soluble in dilute acids and very soluble in ethanol, chloroformand ethyl ether.

Benzocaine is commonly found, particularly in Britain, as an additive in street cocaine and also as a bulking agent in "legal highs". Benzocaine is the most popular cutting agent worldwide, [29] Benzocaine was used in synthesis of leteprinim. Treatment of benzocaine with hydrazine leads to aminostimil - a compound related to isoniazid.

Benzocaine can be prepared by esterification using 4-aminobenzoic acid and ethanol. A bath solution of benzocaine has been used to anesthetize amphibians for surgery. From Wikipedia, the free encyclopedia.During these challenging times, we guarantee we will work tirelessly to support you. We will continue to give you accurate and timely information throughout the crisis, and we will deliver on our mission — to help everyone in the world learn how to do anything — no matter what.

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Updated: September 6, References. Benzocaine is a local anesthetic commonly used for pain relief.


Preparing Benzocaine is often done in a school lab setting to demonstrate the acid-catalyzed esterification of a carboxylic acid with an alcohol, known as Fischer esterification.

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Learn more Explore this Article Steps. Tips and Warnings. Things You'll Need. Related Articles. Add a magnetic stir bar, 1. Add 1mL of concentrated sulfuric acid drop wise with a Pasteur pipette to the ethanol-aminobenzoic solution. A solid will precipitate out of the solution.Benzocaine is a topical anesthetic that helps to numb the pain and itching.

It's used as a topical pain reliever or in cough drops. Benzocaine is the ethyl ester of p-aminobenzoic acid PABA. It can be prepared from PABA and ethanol by Fischer esterification or via the reduction of ethyl p-nitrobenzoate.

Benzocaine is sparingly soluble in water; it is more soluble in dilute acids and very soluble in ethanol, chloroform and ethyl ether. Benzocaine can be prepared by esterfication using 4-aminobenzoic acid and ethanol. It can also be prepared by reduction of ethyl 4-nitrobenzoate to the amine. In industrial practice, the reducing agent is usually iron and water in the presence of a little acid. Benzocaine should be stored in closed bottles, away from moisture and air, if stored for long periods of time.

Benzocaine can be either oxidized with Fenton's reagent or poured down the drain, depending on the amount of waste you intend to dispose.


Jump to: navigationsearch. Ethyl 4-aminobenzoate. Anbesol Orajel Cepacol. Chemical formula. Solubility in water. Navigation menu Personal tools English Log in. Namespaces Page Discussion. Views Read View source View history. Navigation Main page Recent changes Random page Help. This page was last modified on 26 Marchat Privacy policy About Sciencemadness Wiki Disclaimers. Other names Anbesol Orajel Cepacol.

synthesis of benzocaine

Jmol -3D images. Very soluble in chloroformdiethyl etherethanol Soluble in diluted acids.This experiment has two steps.

Step 1: preparation of p-aminobenzoic acid from p-nitrobenzoic acid. Step 2: preparation of ethyl p-aminobenzoate from p-aminobenzoic acid. In step 1 common reduction of aromatic para-nitrobenzoic acid by tin and hydrochloric acid to para-aminobenzoic acid and in step 2 esterification of para-aminobenzoic acid by sulphuric acid and ethanol to benzocaine occurring called Fischer esterification. Aim: To prepare Benzocaine from p- nitrobenzoic acid. Step 1. Step 2. Use: Used as a local anesthetic agent.

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Tin powder. Celite filter aid. Glacial acetic acid. Prepared p-aminobenzoic acid. Absolute ethanol. Sodium carbonate. Reflux condenser set. Gas inlet tube. Buchner funnel. Measuring cylinder. Filter paper. Litmus paper. Step 1 : Preparation of p-aminobenzoic acid. Place 15 g 0. Introduce 35 g 0. Heat the mixture gently until the reaction commences, and remove the flame.

Shake the flask frequently and take care that the insoluble acid adhering to the sides of the flask is transferred to the reaction mixture: occasional gentle warming may be necessary.

After about 20 min, most of the tin will have reacted and a clear solution remains. Allow to cool somewhat and decant the liquid into a 1-litre beaker; wash the residual tin by decantation with 15 ml of water, and add the washings to the contents of the beaker.

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Add concentrated ammonia solution d 0. Transfer the filter cake to a beaker, heat on a water bath with ml of water to ensure extraction of the product and refilter. Concentrate the combined filtrate and washings until the volume has been reduced to ml: filter off any solid which separates. Acidify the liquid to litmus with glacial acetic acid and evaporate on a water bath until crystals commence to separate; cool in ice, filter the crystals at the pump and dry in the steam oven.

The yield of p-aminobenzoic acid, m. Step 2 : Preparation of ethyl p-aminobenzoate esterification of p-aminobenzoic acid. Place 80 ml of absolute ethanol in a ml two-necked flask equipped with a double surface reflux condenser and a gas inlet tube. Pass dry hydrogen chloride through the alcohol until saturated; the increase in weight is about 20 g; remove the gas inlet tube, introduce 12 g 0.

Upon cooling, the reaction mixture sets to a solid mass of the hydrochloride of ethyl p-aminobenzoate.

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It is better, however, to pour the hot solution into ml of water no hydrochloride separates and add solid sodium carbonate carefully to the clear solution until it is neutral to litmus. Filter off the precipitated ester at the pump and dry in the air. The yield of ethyl p-aminobenzoate, m.

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