The Williamson ether synthesis is an organic reactionforming an ether from an organohalide and a deprotonated alcohol alkoxide. This reaction was developed by Alexander Williamson in This reaction is important in the history of organic chemistry because it helped prove the structure of ethers. The general reaction mechanism is as follows: [3]. An example is the reaction of sodium ethoxide with chloroethane to form diethyl ether and sodium chloride:.

The Williamson ether reaction follows an S N 2 bimolecular nucleophilic substitution mechanism. In an S N 2 reaction mechanism there is a backside attack of an electrophile by a nucleophile and it occurs in a concerted mechanism happens all at once.

In order for the S N 2 reaction to take place there colors kannada in usa be a good leaving group which is strongly electronegative, commonly a halide. In the Williamson ether reaction there is an alkoxide ion RO - nca exam notes free acts as the nucleophile, attacking the electrophilic carbon with the leaving group, which in most cases is an alkyl tosylate or an alkyl halide.

The leaving site must be a primary carbon, because secondary and tertiary leaving sites generally prefer to proceed as an elimination reaction. Also, this reaction does not favor the formation of bulky ethers like di-tertbutyl ether, due to steric hindrance and predominant formation of alkenes instead.

The Williamson reaction is of broad scope, is widely used in both laboratory and industrial synthesis, and remains the simplest and most popular method of preparing ethers. Both symmetrical and asymmetrical ethers are easily prepared. The intramolecular reaction of halohydrins in particular, gives epoxides. In the case of asymmetrical ethers there are two possibilities for the choice of reactants, and one is usually preferable either on the basis of availability or reactivity.

The Williamson reaction is also frequently used to prepare an ether indirectly from two alcohols. One of the alcohols is first converted to a leaving group usually tosylatethen the two are reacted together. The alkoxide or aryloxide may be primary, secondary or tertiary.

The alkylating agent, on the other hand is most preferably primary. Secondary alkylating agents also react, but tertiary ones are usually too prone to side reactions to be of practical use.

The leaving group is most often a halide or a sulfonate ester synthesized for the purpose of the reaction. Since the conditions of the reaction are rather forcing, protecting groups are often used to pacify other parts of the reacting molecules e.

The Williamson ether synthesis is a common reaction in the field of Organic Chemistry in industrial synthesis and in undergraduate teaching laboratories. Yields for these ether syntheses are traditionally low when reaction times are shortened, which can be the case with undergraduate laboratory class periods. To help mitigate this issue microwave-enhanced technology is now being utilized to speed up the reaction times for reactions such as the Williamson ether synthesis.

This technology has transformed reaction times that required reflux of at least 1. This methodology helps streamline the synthesis process and makes synthesis on an industrial scale more feasible. The much higher temperature makes the weak alkylating agent more reactive and less likely to produce salts as a byproduct. This method has proved to be highly selective and especially helpful in production of aromatic ethers such as anisole which has increasing industrial applications.

Since alkoxide ions are highly reactive, they are usually prepared immediately prior to the reaction, or are generated in situ. In laboratory chemistry, in situ generation is most often accomplished by the use of a carbonate base or potassium hydroxidewhile in industrial syntheses phase transfer catalysis is very common. A wide range of solvents can be used, but protic solvents and apolar solvents tend to slow the reaction rate strongly, as a result of lowering the availability of the free nucleophile.

For this reason, acetonitrile and NN -dimethylformamide are particularly commonly used. Often the complete disappearance of the starting material is difficult to achieve, and side reactions are common.

Catalysis is not usually necessary in laboratory syntheses. However, if an unreactive alkylating agent is used e. In extreme cases, silver compounds such as silver oxide may be added: [8]. The silver ion coordinates with the halide leaving group to make its departure more facile. Finally, phase transfer catalysts are sometimes used e.Your instructor will give you a handout with pretty detailed instructions.

Alcohols are pretty lousy nucleophiles. But we can make them more nucleophilic by using a base to rip off a proton and give the alcohol a negative charge. A deprotonated alcohol is called an alkoxide.

Bases make alcohols better nucleophiles. Now that we have a decent nucleophile, we can react the alkoxide with an electrophile such as an alkyl halide in an S N 2 reaction to make an ether. Alkoxides react with alkyl halides to form ethers. Williamson ether synthesis is two steps. Be sure to save a little bit of the original starting material mixture to use for a TLC analysis later on!

Afterwards, let the reaction cool and transfer it to a sep funnel to do an extraction with water and ether. Your product is organic soluble and will be in the ether layer, which will be on top you will discard the aqueous layer, which should contain unreacted starting material.

Extraction review: www. Save a little bit of your ether layer for TLC analysis. Then you will let the ether evaporate over a steam bath, which should yield your crude 2-ethoxynaphthalene product.

Finally, you will do a recrystallization using ethanol to purify your product. Recrystallization review: www. Because of this, you can expect your product to have a higher R f value than your starting material. Your TLC will have three spots. One will be your pure starting material, which should be a low riding spot. You will also spot your original reaction mixture, which should contain mostly starting material but may show the presence of a little bit of product.

Your third spot will be the ether layer from the sep funnel. It will contain mostly product, but should contain a little bit of starting material. TLC of alcohol starting material and ether product. After your recrystallization is complete and your product is somewhat dry you will take a melting point.

theoretical yield for williamson ether synthesis of phenacetin

They also want you to take a TLC of your purified product. Melting point review: www.

Theoretical yield for the Williamson ether synthesis of phenacetin?

The limiting reagent in this reaction is 2-hydroxynaphthalene, so that is what you will use to calculate the theoretical yield. Your calculations would look something like this:. Something you should always include in your lab report is a comparison of the IR and NMR spectra of your products and starting materials.

Your product is an ether and so does not contain a hydroxyl group, and this peak will be absent on its IR. The only real difference in the 1 H NMR spectra will be the presence of two ethyl group signals in your product.Please join StudyMode to read the full document. Ganson Ph. D, Revised by Alfredo Mellace Ph. D www. Alcohols are converted into the alkyl halides adding an aqueous solution sodium bromide.

The sulfuric acid acts as a catalyst in converting the OH functional group of butanol, to a better leaving group. In order for this reaction to synthesis 1-Bromobutane, four major methods refluxing, simple distillation, separation, and gravity filtration needs to be performed. Ester also contributes the flavor and aromas in fruits and flowers. The esterification reactions will use in the procedure, which are the interaction of a carboxylic acid with an alcohol, aided by an inorganic acid catalyst H2SO4.

Moreover, the green method will not use any catalyst but using heating source instead microwave. Based on the comparison of two methods, green chemistry is the effective method because reduce the consumption energy and less time consuming than the non-green chemistry preparation. Examples are benzyl acetate, which is finding in orange oil, and isopentyl acetate, which is the part of banana oil. The ester linkage is also present in animal fats and in many biologically important molecules.

Esters can be formed from both organic and inorganic acids and the process of producing an ester is called an Esterification. Esters of organic acids are usually colorless, neutral liquids, pleasant-smelling and generally insoluble in water but readily soluble in organic solvents. Esters are prepared synthetically in large quantities for commercial use as artificial fruit essences Synthesis of Salicylic Acid from Wintergreen Oil Objective — Preparation of salicylic acid organic synthesis from methyl salicylate utilizing previously used procedure from the nineteenth century.

The final product will then be evaluated in comparison to salicylic acid made from benzene. Discussion — In this synthesismethyl salicylate is the starting material or precursor and salicylic acid is the target product. It is the major constituent of wintergreen oil.Sign in. Don't have an account? We weren't able to detect the audio language on your flashcards. Please select the correct language below.

Add to folder [? Find out how you can intelligently organize your Flashcards. You have created 2 folders. Please upgrade to Cram Premium to create hundreds of folders!

Theoretical yield for the Williamson ether synthesis of phenacetin?

Alkyl halide methyl halide is greater than primary alkyl halide which is greater than secondary alkyl halide. Competition between substitution and elimination occurs sterically hindered alkyl halides will undergo E2 instead of SN2.

Flashcards FlashCards Essays. Create Flashcards. Share This Flashcard Set Close. Please sign in to share these flashcards. We'll bring you back here when you are done. Sign in Don't have an account? Set the Language Close. Related Flashcards Acetaminophen Acetaminophen. Add to Folders Close. Please sign in to add to folders.

Upgrade to Cram Premium Close. Upgrade Cancel. Study your flashcards anywhere! How to study your flashcards.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. Chemistry Stack Exchange is a question and answer site for scientists, academics, teachers, and students in the field of chemistry. It only takes a minute to sign up. I think they're asking for the molar yield moles of product obtained divided by moles of limiting reagent used.

The clue is in the fact that they give you the molecular weights. Sign up to join this community. The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered.

Williamson Ether Synthesis Reaction Mechanism

Asked 3 years ago. Active 3 years ago. Viewed times. I've done ether synthesis before but not sure what this is asking Active Oldest Votes. As you can see, it's mathematically equivalent. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Q2 Community Roadmap.The procedure stated in Chem experiment 6 Williamson Ether Synthesis of Phenacetin laboratory manual was followed without any major changes.

Physical appearance for products: On addition of acetaminophen to sodium ethoxide there was a brown coloured solution formed. The crude product obtained was observed to have a beige appearance, and the crystals formed where powdery in texture. On the other hand, the pure recrystallized product gave a shiny white colour appearance, with its crystals being needle like in texture.

Table2- Qualitative analysis using Chromatography. The Rf values of the standards and re-crystallized sample. The TLC results seen in table 2 above were used to determine the true identity of the experimental product. The standard acetaminophen sample spot had a retention factor value of 0. And the spot done for the crude and re-crystallized product gave a retention factor value of 0.

The Mel Temp temperature had a range of C and the standard documented melting point for Phenacetin is C. Discussion: Sodium ethoxide NaOEt was used to react with acetaminophen. K2CO3 is anhydrous, and the Williamson ether synthesis majorly involves the removal of a proton from an alcohol using an SN2 nucleophilic reaction.

When potassium carbonate is present in a solution with acetaminophen it generates the conjugate base of acetaminophen which is powerful enough to pull apart iodoethane. Iodide is left in solution while the CH3CH2 is bonded to acetaminophen and phenacetin is the product.

However, Williamson ether synthesis process requires a strong base such as sodium hydride or sodium metal. Recrystallization requires careful techniques which if not followed properly could lead to loss of recrystallized product. Some loss, resulting from transferring solids from one container to another and leaving a little material behind, cannot be avoided. But it can be ignored by improving the techniques employed in transferring the product. Also, because of the solubility of the solid in the recrystallization solvent, even at low temperatures, any unnecessary prolonged contact with recrystallization solvent, especially if the solvent is not ice-cold will result in loss of product.

For that reason, the following problems commonly occur: if too much solvent is added in the recrystallization, a poor or no yield of crystals will result. If the solid is dissolved below the boiling point of the solution, too much solvent will be needed, resulting in a poor yield. In order to obtain optimal results, a minimum of near-boiling solvent should be used for the recrystallization, and a minimum of ice cold solvent should be used for the rinse.

The recrystallized product was considered to be pure due to the fact that, when ran through the TLC plate, an Rf value of 0. Was obtained which is similar to the Rf value of the standard phenacetin 0.

Acetaminophen produced Rf value of 0. Acetaminophen consists of hydroxyl group which is more polar than phenacetin consisting of ethoxide group. This causes acetaminophen to travel much slowly up the column; phenacetin is more soluble and hence travels faster up the column less affinity to stationary phase in the mobile phase. When the Mel-Temp apparatus was used to observe the melting point of the recrystallized product, it was discovered that the melting point of the experimental phenacetin oC was just a fraction off the literature melting point of phenacetin oCthe mel range of the experimental product is narrow same as the literature melting point thus revealing the purity and the identification of the phenacetin product attained in this experiment.

Phenacetin can also be made by the Schotten-Baumann reaction which is an organic reaction used to convert an acyl halide or anhydride to an amide if reacted with an amine and base. In this reaction there is use of added base to drive the equilibrium in the formation of amides from amines and acid chlorides.

The acylation of amines with carboxylic acid chlorides leads to the production of one equivalent acid, which will form a salt with unreacted amine and diminish the yield.The procedure stated in Chem experiment 6 Williamson Ether Synthesis of Phenacetin laboratory manual was followed without any major changes. Abstract— Recent years have marked the beginning and rapid expansion of the social web, where people can freely express their opinion on different objects such as products, persons, topics etc on blogs, forums or e-commerce sites and opinion analysis is one emerging research field.

Physical appearance for products: On addition of acetaminophen to sodium ethoxide there was a brown coloured solution formed. The crude product obtained was observed to have a beige appearance, and the crystals formed where powdery in texture.

On the other hand, the pure recrystallized product gave a shiny white colour appearance, with its crystals being needle like in texture. Table2- Qualitative analysis using Chromatography. The Rf values of the standards and re-crystallized sample.

Subscribe to RSS

The TLC results seen in table 2 above were used to determine the true identity of the experimental product. The standard acetaminophen sample spot had a retention factor value of 0.

theoretical yield for williamson ether synthesis of phenacetin

And the spot done for the crude and re-crystallized product gave a retention factor value of 0. The Mel Temp temperature had a range of C and the standard documented melting point for Phenacetin is C. Discussion: Sodium ethoxide NaOEt was used to react with acetaminophen. K2CO3 is anhydrous, and the Williamson ether synthesis majorly involves the removal of a proton from an alcohol using an SN2 nucleophilic reaction.

When potassium carbonate is present in a solution with acetaminophen it generates the conjugate base of acetaminophen which is powerful enough to pull apart iodoethane. Iodide is left in solution while the CH3CH2 is bonded to acetaminophen and phenacetin is the product.

Synthesis of Phenacetin from para-Acetamidophenol Essay

However, Williamson ether synthesis process requires a strong base such as sodium hydride or sodium metal. Recrystallization requires careful techniques which if not followed properly could lead to loss of recrystallized product. Some loss, resulting from transferring solids from one container to another and leaving a little material behind, cannot be avoided. But it can be ignored by improving the techniques employed in transferring the product.

Also, because of the solubility of the solid in the recrystallization solvent, even at low temperatures, any unnecessary prolonged contact with recrystallization solvent, especially if the solvent is not ice-cold will result in loss of product. Manufacturing sub-processes are part of the complete process in order to produce the needed goods in production. As VP for operations, part of the responsibilities is to make it sure that the products demanded by the market as articulated by the marketing department are used.

Basically, the for VP operation should be concerned with the production of goods and processed using the necessary For that reason, the following problems commonly occur: if too much solvent is added in the recrystallization, a poor or no yield of crystals will result. If the solid is dissolved below the boiling point of the solution, too much solvent will be needed, resulting in a poor yield.

In order to obtain optimal results, a minimum of near-boiling solvent should be used for the recrystallization, and a minimum of ice cold solvent should be used for the rinse. The recrystallized product was considered to be pure due to the fact that, when ran through the TLC plate, an Rf value of 0. Was obtained which is similar to the Rf value of the standard phenacetin 0. Acetaminophen produced Rf value of 0. Acetaminophen consists of hydroxyl group which is more polar than phenacetin consisting of ethoxide group.

This causes acetaminophen to travel much slowly up the column; phenacetin is more soluble and hence travels faster up the column less affinity to stationary phase in the mobile phase. When the Mel-Temp apparatus was used to observe the melting point of the recrystallized product, it was discovered that the melting point of the experimental phenacetin oC was just a fraction off the literature melting point of phenacetin oCthe mel range of the experimental product is narrow same as the literature melting point thus revealing the purity and the identification of the phenacetin product attained in this experiment.

Phenacetin can also be made by the Schotten-Baumann reaction which is an organic reaction used to convert an acyl halide or anhydride to an amide if reacted with an amine and base.

theoretical yield for williamson ether synthesis of phenacetin

Planning Aim of experiment: The aim of this experiment is to investigate the rate of reaction of an acid with a rock. There are different factors that effect the rate of reaction between calcium carbonate marble chips and hydrochloric acid.

The factor that concerns my investigation is the concentration of the liquid reactant, which in this case is the hydrochloric acid. The aim is to experiment In this reaction there is use of added base to drive the equilibrium in the formation of amides from amines and acid chlorides. The acylation of amines with carboxylic acid chlorides leads to the production of one equivalent acid, which will form a salt with unreacted amine and diminish the yield.


Replies to “Theoretical yield for williamson ether synthesis of phenacetin”

Leave a Reply

Your email address will not be published. Required fields are marked *