Which alcohol oxidizes faster

It may not mix easily, and two distinct layers might be left in the container. The alcohols can also be oxidised without combustion to produce carboxylic acids. For example, ethanol can be oxidised to ethanoic acid using an oxidising agent. Each of the two oxygen atoms provided by the oxidising agent are shown as [O]. Notice that the left-hand side of the ethanol molecule is unchanged. The reaction involves the -OH group on the right-hand side.

Propanol is oxidised by heating with an oxidising agent. Name the carboxylic acid formed in the reaction. Propanoic acid. There is no reaction whatsoever.

If you look at what is happening with primary and secondary alcohols, you will see that the oxidising agent is removing the hydrogen from the -OH group, and a hydrogen from the carbon atom attached to the -OH. Tertiary alcohols don't have a hydrogen atom attached to that carbon. You need to be able to remove those two particular hydrogen atoms in order to set up the carbon-oxygen double bond. First you have to be sure that you have actually got an alcohol by testing for the -OH group.

You would need to show that it was a neutral liquid, free of water and that it reacted with solid phosphorus V chloride to produce a burst of acidic steamy hydrogen chloride fumes. Note: You will find the chemistry of the phosphorus V chloride test by following this link. You would then add a few drops of the alcohol to a test tube containing potassium dichromate VI solution acidified with dilute sulphuric acid.

The tube would be warmed in a hot water bath. In the case of a primary or secondary alcohol, the orange solution turns green. With a tertiary alcohol there is no colour change. You need to produce enough of the aldehyde from oxidation of a primary alcohol or ketone from a secondary alcohol to be able to test them. There are various things which aldehydes do which ketones don't. These include the reactions with Tollens' reagent, Fehling's solution and Benedict's solution, and are covered on a separate page.

Note: You will find these tests for aldehydes by following this link. In my experience, these tests can be a bit of a bother to carry out and the results aren't always as clear-cut as the books say. A much simpler but fairly reliable test is to use Schiff's reagent.

Schiff's reagent isn't specifically mentioned by any of the UK-based syllabuses, but I have always used it. Schiff's reagent is a fuchsin dye decolourised by passing sulphur dioxide through it.

In the presence of even small amounts of an aldehyde, it turns bright magenta. It must, however, be used absolutely cold, because ketones react with it very slowly to give the same colour. If you heat it, obviously the change is faster - and potentially confusing. While you are warming the reaction mixture in the hot water bath, you can pass any vapours produced through some Schiff's reagent.

If the Schiff's reagent quickly becomes magenta, then you are producing an aldehyde from a primary alcohol. If there is no colour change in the Schiff's reagent, or only a trace of pink colour within a minute or so, then you aren't producing an aldehyde, and so haven't got a primary alcohol. Because of the colour change to the acidified potassium dichromate VI solution, you must therefore have a secondary alcohol.

You should check the result as soon as the potassium dichromate VI solution turns green - if you leave it too long, the Schiff's reagent might start to change colour in the secondary alcohol case as well. Water is not present when the PCC reagent is used, so the oxidation stops at the aldehyde stage. In both solvents allylic alcohols are oxidized efficiently to conjugated enals and enones respectively.

To learn more about these Click Here. Compounds in which a hydroxyl group is bonded to an aromatic ring are called phenols. The chemical behavior of phenols is different in some respects from that of the alcohols, so it is sensible to treat them as a similar but characteristically distinct group. A corresponding difference in reactivity was observed in comparing aryl halides, such as bromobenzene, with alkyl halides, such as butyl bromide and tert-butyl chloride.

Thus, nucleophilic substitution and elimination reactions were common for alkyl halides, but rare with aryl halides. On the other hand, substitution of the hydroxyl hydrogen atom is even more facile with phenols, which are roughly a million times more acidic than equivalent alcohols. This phenolic acidity is further enhanced by electron-withdrawing substituents ortho and para to the hydroxyl group, as displayed in the following diagram.

The alcohol cyclohexanol is shown for reference at the top left. It is noteworthy that the influence of a nitro substituent is over ten times stronger in the para-location than it is meta, despite the fact that the latter position is closer to the hydroxyl group.

Furthermore additional nitro groups have an additive influence if they are positioned in ortho or para locations. The trinitro compound shown at the lower right is a very strong acid called picric acid. Why is phenol a much stronger acid than cyclohexanol? To answer this question we must evaluate the manner in which an oxygen substituent interacts with the benzene ring.

As noted in our earlier treatment of electrophilic aromatic substitution reactions, an oxygen substituent enhances the reactivity of the ring and favors electrophile attack at ortho and para sites. It was proposed that resonance delocalization of an oxygen non-bonded electron pair into the pi-electron system of the aromatic ring was responsible for this substituent effect.

Formulas illustrating this electron delocalization will be displayed when the "Resonance Structures" button beneath the previous diagram is clicked. A similar set of resonance structures for the phenolate anion conjugate base appears below the phenol structures. The resonance stabilization in these two cases is very different.

An important principle of resonance is that charge separation diminishes the importance of canonical contributors to the resonance hybrid and reduces the overall stabilization.

The contributing structures to the phenol hybrid all suffer charge separation, resulting in very modest stabilization of this compound.

On the other hand, the phenolate anion is already charged, and the canonical contributors act to disperse the charge, resulting in a substantial stabilization of this species. The conjugate bases of simple alcohols are not stabilized by charge delocalization, so the acidity of these compounds is similar to that of water.

An energy diagram showing the effect of resonance on cyclohexanol and phenol acidities is shown on the right. Since the resonance stabilization of the phenolate conjugate base is much greater than the stabilization of phenol itself, the acidity of phenol relative to cyclohexanol is increased.

Supporting evidence that the phenolate negative charge is delocalized on the ortho and para carbons of the benzene ring comes from the influence of electron-withdrawing substituents at those sites. The additional resonance stabilization provided by ortho and para nitro substituents will be displayed by clicking the "Resonance Structures" button a second time. You may cycle through these illustrations by repeated clicking of the button.

As with the alcohols, the phenolic hydroxyl hydrogen is rather easily replaced by other substituents. For example, phenol reacts easily with acetic anhydride to give phenyl acetate.

Likewise, the phenolate anion is an effective nucleophile in S N 2 reactions, as in the second example below. The facility with which the aromatic ring of phenols and phenol ethers undergoes electrophilic substitution has been noted. Two examples are shown in the following diagram.

The second reaction is interesting in that it further demonstrates the delocalization of charge that occurs in the phenolate anion.

Carbon dioxide is a weak electrophile and normally does not react with aromatic compounds; however, the negative charge concentration on the phenolate ring enables the carboxylation reaction shown in the second step. The sodium salt of salicylic acid is the major product, and the preference for ortho substitution may reflect the influence of the sodium cation.

This is called the Kolbe-Schmidt reaction , and it has served in the preparation of aspirin, as the last step illustrates. Phenols are rather easily oxidized despite the absence of a hydrogen atom on the hydroxyl bearing carbon. Among the colored products from the oxidation of phenol by chromic acid is the dicarbonyl compound para-benzoquinone also known as 1,4-benzoquinone or simply quinone ; an ortho isomer is also known.

These compounds are easily reduced to their dihydroxybenzene analogs, and it is from these compounds that quinones are best prepared. Note that meta-quinones having similar structures do not exist.