In this experiment, dehydration is carried out using cyclohexanol to obtain cyclohexene. This acid-catalysed reaction involves E1 elimination mechanism. The dehydration of alcohol will remove OH- from cyclohexanol to form cyclohexene. Cyclohexene contains a single double bond in the molecule. It is a six carbon aromatic hydrocarbon. Phosphoric acid is mixed with cyclohexanol in the round-bottomed flask and is heated. The phosphoric acid act as a catalyst that increases the rate of reaction but it does not change the overall stoichiometry. The acid catalyst will convert the hydroxyl group into a good leaving group. It is an equilibrium reaction in which the equilibrium is forced to the right (alkene). (Department of Chemistry 2014) Boling chips are added to the distillating flask. If not, the liquid may over boil and shoot out of the …show more content…
E1 reaction is a two-step mechanism which includes the protonation of hydroxyl group and the formation of carbocation intermediate (rate-determining step).
Questions:
1. Dehydration of cyclohexanol gives cyclohexene. Draw mechanism for the reaction.
2. What alkene(s) will be produced when each of the following alcohols is dehydrated?
a) t-butyl alcohol CH3 CH3 CH3 C OH CH3 C = CH2 + H2O CH3 Ans: 2-methyl-1-propene
b) 3-methylcyclohexanol
Ans: 1-methylcyclohexene, 3-methylcyclohexene and 4-methylcyclohexene.
3. The dehydration of 3,3-dimethyl-2-butanol yields three different products. Write equations to show how carbocation rearrangements explain two of the products.
Ans: A secondary carbocation is formed initially, it then rearranges to a tertiary carbocation when a neighbouring methyl group with its bonding electron pair migrates to the positive carbon. The charge is transferred to the tertiary
The objective of this lab was to create a ketone through an oxidation reaction using a using a secondary alcohol and oxidizing agent in order to use that ketone in a reduction reaction with a specific reducing agent to determine the affect of that reducing agent on the diastereoselectivity of the product. In the first part of this experiment, 4-tert-butylcyclohexanol was reacted with NaOCl, an oxidizing agent, and acetic acid to form 4-tert-butylcyclohexanone. In the second part of this experiment, 4-tert-butylcyclohexanone was reacted with a reducing agent, either NaBH4 in EtOH or Al(OiPr)3 in iPrOH, to form the product 4-tert-butylcyclohexanol. 1H NMR spectroscopy was used to determine the cis:trans ratio of the OH relative to the tert-butyl group in the product formed from the reduction reaction with each reducing agent. Thin-layer chromatography was used in both the oxidation and reduction steps to ensure that each reaction ran to completion.
4. Write a structural diagram equation to represent the reaction between each alcohol and HCl(aq).
This way, cyclohexane is converted to adipic acid or hexanedioic acid. Since the product is soluble in hot water, the two-phase systems (organic cyclohexane and aqueous hydrogen peroxide) slowly become a single aqueous phase. In the end, only H2O2 and cyclohexene can be changed, tungstate and the phase transfer catalyst can be tapped and reused. The phase transfer catalyst used were a mixture of aliquat 336 and potassium hydrogen sulphate.
A reaction of the Grignard reagent and carbon dioxide results in an acid, and reaction of a nitrile and a Grignard reagent produce a carbonyl via an imine intermediate. These are show below, respectively.
Alcohol dehydrations are widely used in many industries to produce alkene. In this experiment 2-methylcyclohexanol was dehydrated to three possible products using phosphoric acid as a catalyst. The main tool for this experiment is the Hickman still. First, Drierite was added to the Hickman still so that any excess water formed during the experiment will be absorbed. It also acted as a boiling stone and addition surface to increase surface area. Next, 0.75 mL of 2-methylcyclohexanol is added to the still and right after 1 mL of phosphoric acid is added. The phosphoric acid (H3PO4) acts as a catalyst in order for the reaction to occur. The mixture is heated up to between 120o Celsius and 160o Celsius. If the temperature goes above 165oC then
Abstract: Using hypochlorous acid to convert secondary alcohol called cyclododecanol to the corresponding ketone which is cyclododecanone by oxidation.
2) What two chemicals are given out when carbohydrates are burned? If carbohydrates (made of carbon, hydrogen, and oxygen)
The purpose of this lab was to carry out a dehydration reaction of 2-methylcyclohexanol by heating it in the presence of phosphoric acid and determining which alkene product would be the major product. Methylcyclohexanols were dehydrated in an 85% phosphoric acid mixture to yield the minor and major alkene product by elimination reaction, specifically E1. The alkenes were distilled to separate the major and minor products and gas chromatography was used to analyze the results and accuracy of the experiment. The hypothesis was the major product of the reaction would be the most substituted product. This conclusion was made because of
In a bimolecular nucleophilic substitution or SN2 reaction, there is only one-step. This occurs because the addition of the nucleophile and the elimination of the leaving group spontaneously occur at the same time.
SN1 reactions are considered unimolecular nucleophilic substitution mechanisms and are a first-order process. Meaning that the reaction forms a carbocation intermediate and that the concentration of the nucleophile does not play a role in the rate-determining step, which is the slowest step in the reaction. All of the SN1 reaction mechanisms in this procedure can react two different ways. The expected mechanism for these reactions would be that the carbocation would react with the weak nucleophile nitrate, attaching the nitrogen to the positively charged carbon. However, while nitrate is the intended nucleophile in all of the reactions, it is a poor nucleophile. The ethanol used in this reaction is a polar protic ionizing solvent,
The initial product is the beta-hydroxyketone, which rapidly undergoes dehydration and creates the final product, trans-p-anisalacetophenone. Technically, both the carbonyls cannot be mixed together with sodium hydroxide to get one product. We will get a dominant product of trans-p-anisalacetophenone. This reaction is an exception and we get away with it. P-anisaldehyde and acetophenone together only make one enolate. This helps our exception, but there are still two carbonyls. With our weak base, we should be worried about acetophenone reacting with itself but we are not. This is due to steric hindrance, like I stated earlier. Aldehydes are better electrophilic carbons and therefore the ketone will react with the aldehyde faster than reacting with itself. It will quickly form the product trans-p-anisalacetophenone because it is the favored product. We do not have to use expensive LDA, we can use the weaker base and get away with it.
Mechanism: Key features of the Fischer Esterification mechanism are: a. protonation of the carbonyl group, b. the
The reaction is an electrophilic aromatic substitution, the hydrogen atom of the aromatic ring is replaced as a consequence of an electrophilic attack on the aromatic benzene ring. (chem.ucla.edu, 2015) An electrophile attacks the pi electrons of the benzene ring from acetanilide, and this forms a resonance which stables the carbocation. The carbocation is attacked and it loses a proton.
2nd step involves the carbocation intermediate being attacked by water that acts as a nucleophile to form protonated alcohol intermediate. This is the fast step and does not determine rate of reaction.
SN1 is a limiting mechanism that is a unimolecular nucleophic substation reaction. In this mechanism it involves two steps, one in which the leaving group leaves and then forms a carbocation intermediate, shown in figure 2. Then it is able to break bonds between carbon and making it able for carbon to leave the group before the bond forming with nucleophile begins1.