Carbocation Essays

Observations The purpose of this experiment was to be able to synthesize triphenylmethyl bromide from triphenylmethanol by a trityl carbocation intermediate. During the experiment, 0.100 g of triphenylmethanol was placed into a small test tube. The triphenylmethanol looked like a white powder. Next 2 mL of acetic acid was added to the test tube and the solution turned a cloudy white color. There was a strong odor similar to the smell of vinegar given off. After the solution was heated and the solid

dependent on both the concentration of the nucleophile and alkyl halide. The following figure displays the general mechanism for a SN2 reaction. The SN1 reaction mechanism is stepwise meaning that the leaving group departs first to create a carbocation intermediate, which later bonds with the nucleophile. The rate of this reaction is just dependent on the concentration of the alkyl halide.1 The following figure displays the general mechanism for a SN2 reaction. When comparing these

formation of a carbocation from the loss of a leaving group, the second being a rapid attack on the carbocation by the nucleophile. The term unimolecular can be used to describe this type of reaction since there is only one organic substance involved in the rate determining step. (3) Since the rate of the reaction is not dependent upon the nucleophile concentration, the rate determining step for this process would be the loss of the leaving group resulting in the formation of a carbocation. The stability

consist of one reactant. The rate of the reaction is solely dependent on one reactant and the process occurs in two steps. In these two steps the leaving group will leave and allow the substrate to produce a carbocation intermediate. Secondly the nucleophile then prepares itself to attack the carbocation that was formed, in order to produce the final product. In these reactions there is a slow step and a fast step on how the mechanism can be carried out. An example of the slow step and fast will be provided

If carbocations rearrange during the intermediate phase, the product obtained will be a partial racemic mixture, where the maximum amount of product reflects the most stable carbocation intermediate thru rearrangement. Due to the relative stability of the carbocation, only tertiary alkyl halides can perform SN1 reactions, as shown below. Primary, secondary, and tertiary alcohols can react through substitution but only with hydrobromic acid (HBr), hydrochloric acid (HCl) and hydroiodic acid (HI)

In organic and inorganic chemistry, nucleophilic substitution reactions are the most well studied and useful class of reactions. These reactions can occur by a range of mechanisms, the two studied in this lab are the SN1 and SN2 reactions. In a nucleophilic substitution, the nucleophile is a electron rich chemical species which attacks the positive charge of an atom to replace a leaving group. Since nucleophiles donate electrons, they are defined as Lewis bases. The positive or partially positive

causes the formation of a carbocation and an alkene will form near the charge. Based on the position of the charge, two or three products can be produced. After the protonation of the alcohol group on 2-methylcyclohexanol, resulting in water (good leaving group), a double bond will form, producing 3-methylcoyclohexene.

Dehydration of 2-Methylcyclohexanol Sura Abedali Wednesday 2:00 PM January 31, 2018 Introduction: Dehydration reactions are important processes to convert alcohols into alkenes. It is a type of elimination reaction that removes an “-OH” group from one carbon molecule and a hydrogen from a neighboring carbon, thus releasing them as a water molecule (H2O) and forming a pi bond between the two carbons1. In this experiment, 2-methylcyclohexanol undergoes dehydration to form three possible products:

dehydration and dehydrobromination undergo the elimination reaction, which includes E1 and E2 reaction. E1 is unimolecular elimination, which is removing H-X substituent to form a double bonds. The mechanism of E1 reaction includes 2 steps, formation of carbocation and deprotonation. E2 is bimolecular elimination, which is the removal of two substituent groups to form an alkene. The hydrogen removed must be anti to the leaving group. The mechanism of E2 reaction has only one steps, which is displacement of

the OH leaving group, thus turning it into water, a suitable leaving group. After the water molecule departed, the carbocation can form two of the three products, 1-methylcyclohexene and 3-methylcyclohexene, by the elimination of an H on an adjacent carbon. Alternatively, the carbocation can undergo rearrangement, forming a 3° carbocation. As a result, this more stable carbocation forms methylenecyclohexane and

configurations at reaction centers. This is because this reaction proceeds through a stable carbocation intermediate and the carbon at the reaction center goes to sp2 hybridized state (planar geometry). The incoming nucleophile can attack from both sides of the plane and can give two products with retained and inverted configuration. If there is a partial interaction with the leaving group (nucleofuge) with carbocation there will be more product with inverted configuration and if there is no interaction

For this experiment, a nitro arene was prepared and then the relative rates of bromination for a set of arenes was observed. Electrophilic aromatic substitution is the reaction of an electrophile with an aromatic ring to form a new bond between the aromatic ring and the electrophile. Two experiments were performed. First, the preparation of 4-nitro-1-bromobenzene takes place through a nitration of bromobenzene. The bromobenzene in this reaction will be treated with both sulfuric and nitric acid

This is beneficial for reactivity because the nitrogen in -NH2 in aniline is able to delocalize the positive charge of a carbocation by donating its electrons to the carbon during the transition state when aniline is brominated. The next strongest substituent would be -OH in phenol, followed by -OCH3 in anisole. This is because the three hydrogens on the carbon make the carbon

In the first step, the leaving group departs, forming a carbocation C+. In the second step, the nucleophilic reagent (Nuc :) attaches to the carbocation and forms a covalent sigma bond. If the substrate has a chiral carbon, this mechanism can result in either inversion of the stereochemistry or retention of configuration. Usually both occur without preference

The acid-catalysed dehydration of a secondary and primary alcohol revealed that the E1 mechanism undergoes and favors rearrangement for a more stable carbocation; this reaction favors a Zaitsev product, which attacks the most substituted beta hydrogen. The base-induced dehydration of a secondary and primary bromide undergoes an E2 mechanism and favors a Hoffman product because of the presence of a sterically

leaving group. Alcohols react with substances like HCl and HBr during substitution reactions because alcohol is not a good leaving group. Determining if the reaction will be SN1 or SN2 is based on the structure of the alcohol and which way the carbocation forms. The solvent also plays a role in what the product will form. If there is a polar aprotic solvent, the reaction will be SN1 and will produce a different product than if a polar aprotic solvent was used, which will be an SN2 reaction. All these

 Unimolecular - rate depends on concentration of only the substrate.  Does NOT occur with primary alkyl halides (leaving groups).  Strong acid can promote loss of OH as H2O or OR as HOR if tertiary or conjugated carbocation can be synthesized.15 Comparison of Enolization and Nucleophilic Reactions Enolization Nucleophilic Reactions 1) In this type of reaction tautomerism happens. 1) In these types of reactions there is no phenomenon of tautomerism is happens. 2) They

halide group to form a carbocation intermediate. This is the rate determining step, and it is also the slowest step. In the second step a nucleophile attacks a face of the the carbocation. Figure 1 displays this mechanism. Only one molecule, the substrate, determines the rate determining step in an SN1 reaction. The nucleophile has no relevance to the rate law in this reaction. The structure of the substrate play a key role in SN1 reaction. Since SN1 reaction form a carbocation intermediate, the reaction

This helps to indicate whether or not the reaction follows Markovnikov’s Rule, which states that the electrophile (E+) will add to the carbon involved in a double bond that produces the most stable carbocation. If the rule is followed, the reaction will proceed according to the mechanism in Figure 1. In the silver nitrate test, the alkyl bromide is added to AgNO3. The rate of precipitation with 2° should be faster than the solution with the 1° alkyl halide

following molecules with a nucleophile. Explain whether the given molecule would react by S_N 1 or S_N 2 mechanism and explain why. 1-methyl-1-bromo-cyclohexane: S_N 1 mechanism because after Br leaves (leaving group departure) then it is a tertiary carbocation which is favored more in this type of mechanism. 1-bromopropane: This would react by S_N 2 mechanism because it is a primary alkyl halide, which undergo this type of mechanism. Also the nucleophile will be able to attack better because of its structure