Why is tertiary alcohol more reactive

However, in the case of an alcohol , the alkyl group will "push" electrons towards the oxygen; this will increase the electron density on the oxygen atom and reduce the pull the atom has on the two bonding electrons it shares with the acidic proton. Tertiary alcohols are more reactive because the increased number of alkyl groups increases effect.

Still, ethanol has the ability to act as an acid because of the ability to donate it's hydroxyl proton. However, aqueous solutions of ethanol are slightly basic. This is is because the oxygen in ethanol has lone electron pairs capable of accepting protons, and thus ethanol can act as a weak base. Originally Answered: What is the pH of alcohol? Why is tertiary alcohol more stable? Category: science chemistry.

Does more stable mean more reactive? Why tertiary alcohol is most reactive? Are tertiary Carbocations more reactive? Which is most stable carbocation? Is a secondary allylic carbocation more stable than a tertiary carbocation? What makes a stable carbocation?

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We receieved your request Stay Tuned as we are going to contact you within 1 Hour Close. Thank you for registering. One of our academic counsellors will contact you within 1 working day. Please check your email for login details. Since oxygen is slightly more electronegative than chlorine 3. Despite this promising background evidence, alcohols do not undergo the same S N 2 reactions commonly observed with alkyl halides.

For example, the rapid S N 2 reaction of 1-bromobutane with sodium cyanide, shown below, has no parallel when 1-butanol is treated with sodium cyanide.

In fact ethyl alcohol is often used as a solvent for alkyl halide substitution reactions such as this. The key factor here is the stability of the leaving anion bromide vs.

We know that HBr is a much stronger acid than water by more than 18 powers of ten , and this difference will be reflected in reactions that generate their conjugate bases. The weaker base, bromide anion, is more stable and its release in a substitution or elimination reaction will be much more favorable than that of hydroxide ion, a stronger and less stable base.

Clearly, an obvious step toward improving the reactivity of alcohols in S N 2 reactions would be to modify the —OH functional group in a way that improves its stability as a leaving anion. The only problem with this strategy is that many nucleophiles, including cyanide, are deactivated by protonation in strong acid, effectively removing the nucleophilic co-reactant needed for the substitution. The strong acids HCl, HBr and HI are not subject to this difficulty because their conjugate bases are good nucleophiles and are even weaker bases than alcohols.

The following equations illustrate some substitution reactions of alcohols that may be effected by these acids. The numbers in parentheses next to the mineral acid formulas represent the weight percentage of a concentrated aqueous solution, the form in which these acids are normally used. Although these reactions are sometimes referred to as "acid-catalyzed" this is not strictly correct. In the overall transformation a strong HX acid is converted to water, a very weak acid, so at least a stoichiometric quantity of HX is required for a complete conversion of alcohol to alkyl halide.

The necessity of using equivalent quantities of very strong acids in this reaction limits its usefulness to simple alcohols of the kind shown above. Alcohols having acid sensitive groups would, of course, not tolerate such treatment.

Nevertheless, the idea of modifying the -OH functional group to improve its stability as a leaving anion can be pursued in other directions. The following diagram shows some modifications that have proven effective. In each case the hydroxyl group is converted to an ester of a strong acid. The first two examples show the sulfonate esters described earlier.

The third and fourth examples show the formation of a phosphite ester X represents remaining bromines or additional alcohol substituents and a chlorosulfite ester respectively. All of these leaving groups colored blue have conjugate acids that are much stronger than water by 13 to 16 powers of ten so the leaving anion is correspondingly more stable than hydroxide ion.

The mesylate and tosylate compounds are particularly useful in that they may be used in substitution reactions with a wide variety of nucleophiles. The intermediates produced in reactions of alcohols with phosphorus tribromide and thionyl chloride last two examples are seldom isolated, and these reactions continue on to alkyl bromide and chloride products.

The importance of sulfonate ester intermediates in general nucleophilic substitution reactions of alcohols may be illustrated by the following conversion of 1-butanol to pentanenitrile butyl cyanide , a reaction that does not occur with the alcohol alone see above. The phosphorus and thionyl halides, on the other hand, only act to convert alcohols to the corresponding alkyl halides. Some examples of alcohol substitution reactions using this approach to activating the hydroxyl group are shown in the following diagram.

Just how these enzymes function obviously is of great interest and importance. If the role of phosphate esters, such as ATP, in carrying out reactions such as esterification in aqueous media under the influence of enzymes in cells is not clear to you, think about how you would try to carry out an esterification of ethanol in dilute water solution.

Remember that, with water in great excess, the equilibrium will be quite unfavorable for the esterification reaction of Equation The phosphate esters provide this function in biochemical systems by being quite unreactive to water but able to react with carboxylic acids under the influence of enzymes to give acyl phosphates.

These acyl phosphates then can react with alcohols under the influence of other enzymes to form esters in the presence of water. John D. Robert and Marjorie C.

Caserio Basic Principles of Organic Chemistry, second edition. Benjamin, Inc. ISBN This content is copyrighted under the following conditions, "You are granted permission for individual, educational, research and non-commercial reproduction, distribution, display and performance of this work in any format.

Addition of 1 mole of an alcohol to 1 mole of thionyl chloride gives an unstable alkyl chlorosulfite, which generally decomposes on mild heating to yield the alkyl chloride and sulfur dioxide: Chlorides can be prepared in this way from primary and secondary, but not tertiary, alcohols. Dehydration of Alcohols with Strong Acids In the reaction of an alcohol with hot concentrated sulfuric acid, the alcohol is dehydrated to an alkene: This is the reverse of acid-catalyzed hydration of alkenes discussed previously Section E and goes to completion if the alkene is allowed to distill out of the reaction mixture as it is formed.

Diethyl ether is made commercially by this process: Most alcohols also will dehydrate at fairly high temperatures in the presence of solid catalysts such as silica gel or aluminum oxide to give alkenes or ethers.

Carbocation Rearrangements Rearrangement of the alkyl groups of alcohols is very common in dehydration, particularly in the presence of strong acids, which are conducive to carbocation formation. Typical examples showing both methyl and hydrogen migration follow: The key step in each such rearrangement is isomerization of a carbocation, as discussed in Section B.

The most important phosphate esters are derivatives of mono-, di-, and triphosphoric acid sometimes classified as ortho-, pyro-, and meta-phosphoric acids, respectively : The equilibrium between the esters of any of these phosphoric acids and water favors hydrolysis: However, phosphate esters are slow to hydrolyze in water unless a catalyst is present. The energy so stored is used in other reactions, the net result of which is hydrolysis: The substance that is the immediate source of energy for many biological reactions is adenosine triphosphate ATP.

Contributors and Attributions John D.