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## Hot answers tagged phenols

48

Nope. Alcohols consist of an -$\ce{OH}$ group bonded to a saturated carbon ($\mathrm{sp^3}$ hybridized, no multiple bonds). IUPAC says: alcohols Compounds in which a hydroxy group, -$\ce{OH}$, is attached to a saturated carbon atom $\ce{R3COH}$. The term 'hydroxyl' refers to the radical species, $\ce{HO^.}$. and phenols Compounds having one ...

24

Like aniline, phenol too reacts to a very less extent during Friedel-Crafts reaction. The reason being that the oxygen atom of phenol has lone pair of electrons which coordinate with Lewis acid. In fact most substituents with lone pair would give poor yield. The two pathways involved in the reaction with phenol reduce the overall yeild: Phenols ...

20

In fact I find a more simple reasoning with resonance structure. When phenol loses the $\ce{H+}$ the phenolate ion is stabilized due to the resonance effect, as shown below: The energy of the dissociated form is lower and so phenol has more chance to be in the solution dissociated with the phenolate ion. Aliphatic alcohols are not stabilized by resonance so ...

18

The effect is indeed amazing, if you compare the $\mathrm{p}K_\mathrm{a}$ of tert-butanol (17.0) with that of phenol (9.95). Deprotonation is facilitated when the reaction goes downhill (energywise). In order to obtain stabilization of the anion, the negative charge needs to be distributed over a larger number of centres. This distribution (only) is ...

17

I would appreciate learning whether such reasoning, for these two type of substituted phenols is plausible or whether furthermore solid arguments should be invoked. Your reasoning seems generally well thought out. You clearly have a good understanding of inductive effects and you mention resonance effects in the cresol series. Structural effects don't ...

13

The reaction is demethylation of methoxybenzene. You can do it by using an acid which has a nucleophilic counter ion. It is not actually obvious why the iodine nucleophile attacks the methyl group and not inside benzene ring. The other option would be: This reaction doesn't happen because otherwise the iodine ion would appear inside the benzene ring ...

12

To add to @user223679's answer. Phenol can react via two pathways with acyl chlorides to give either esters, via O-acylation, or hydroxyarylketones, via C-acylation. However, phenol esters also undergo a Fries rearrangement under Friedel-Crafts conditions to produce the C-alkylated, hydroxyarylketones. This reaction is promoted by having an excess of ...

11

There are actually several factors that affect the stabilization of negative charge. The first is what kind of atom centers the charge can be delocalized on and the second factor is how many atom centers the charge can be delocalized on. The first factor is more important than the second. Just think it like quality is more important than quantity. Symmetry ...

11

The acidity of nitrophenols (or any acid for that matter) is determined by the stability of the conjugate base. In the case of m-nitrophenol and p-nitrophenol, the relative stability can be determined by looking at the resonance structures. You can see that p-nitrophenol has an additional resonance structure where the negative charge is delocalised onto the ...

11

You have correctly identified that m-nitrophenol should be the weakest acid among the isomers as the resulting anion cannot be stabilised by the $\text{-M}$ effect of nitro group owing to its meta location. The acidity order of the remaining two nitrophenols can be explained in this way: Hydrogen bonding is possible in both of them. But note that: $$\... 10 You can always fractionally distillate the two. In this case, since the boiling points have a large difference, simple distillation works as well. (I'm not too good with "collateral damage" of reactions, so if a reaction affects an extra group that it shouldn't, please let me know) Otherwise, you can use the Claisen rearrangement to protect the ortho ... 10 This can be done by first reating the phenol with \ce{HNO2} Which gives us this Then reacting with dil \ce{HNO3} we get 90% yield of para nitro phenol This happens because \ce{N=O} has a very strong - I effect thus it concentrates the electrons more towards the para position so on reacting with dil \ce{HNO3} we get max yield of para P.... 10 a phenol will not react (or react very slowly) with \ce{PCl5} That's not true. Phenol and \ce{PCl5} do react, producing mixture of compounds of formula \ce{PCl_n(C6H5O)_{5-n}} (with n > 1 ). It is even possible to produce \ce{(C6H5O)5P}![1] However, unlike in alcohols, in phenols: the carbon–oxygen bond is much stronger, having a bond order ... 10 After doing some looking around, and going back to check what I thought I knew about coordination complexes, I think I understand why you're seeing two equations. I first recommend reading the pages on Chemguide that talk about coordination chemistry, particularly the first half of this page on acidity, and the pages on reactions with hydroxide and ammonia. ... 10 As an acidic compound, phenol started to degrade the protective layers of your skin, and partially diffused into deeper layers. This, and because of the moderate solubility in water are the reason the scent of phenol was still recognisable after some time. While phenol is better soluble in ethanol and methanol, one refrains from these solvents to clean the ... 10 With unsubstituted phenol (\ce{PhOH}) dark-brown precipitation is formed:$$\ce{(NH4)2[Ce(NO3)6] + 2 PhOH -> [Ce(NO3)4(PhOH)2] + 2 NH4NO3}$$Other phenols should produce wine-red solution as expected [1, p. 478]. Also, this and other phenol tests are discussed in [2]. Pavia, D. L. A small-scale approach to organic laboratory techniques, 3rd Ed.; ... 10 This is not really an answer to your question, but I do not think that it is possible to answer it. From one of the many comments we learn that the reference is actually the "preparation of piperonal". It uses 3-4-dihydroxy-benzenecarbaldehyde instead of catechol, but the reaction is same, with \ce{CH2I2} and \ce{NaOH}. I was able to find this reaction ... 9 I don't understand why two different products are formed in the same reaction using very similar bases. If the bases make a a difference, there must be a difference between them. If the anion is the same, the cation must make the difference. The difference between \ce{Na+} and \ce{K+} lies in the ionic radii of 0.95 and 1.33 \mathring{A}, ... 9 Let me answer the second question first, because the answer is so much easier: Of course the hydrogen bond strength depends among others upon the carbon oxygen is attached to. Consider phenol and methanol or methanol and formic acid. The guess as to which hydrogen bond is stronger is — I have to admit it — my speculation. But I think that methanol should be ... 9 There is a lot of good thinking in your proposed synthetic strategy. The one major shortcoming is, as @Mithoron points out, \ce{OH^{-}} is not an electrophile. We need to introduce a methyl, hydroxy and nitro group onto a benzene ring. If we look into our synthetic "toolbox" here are some thoughts that might come to mind: A methyl group can be readily ... 9 Ludwig Gattermann's The Practical Methods of Organic Chemistry (translated into English, 1896) has two references to reduction of aromatics with zinc dust: The first one refers to Liebigs Annalen, issue 140, page 295 (1866): Ueber die Reduction aromatischer Verbindungen mittelst Zinkstaub, Adolf Baeyer This roughly translates to "On the reduction of ... 8 Boron tribromide is a standard reagent for cleaving aryl methyl ethers to the corresponding phenol. It is a general method and can be used in aromatic methyl ethers with sensitive substituents where acid or base cannot be tolerated. The above Wiki link also shows the following mechanism 1) complex or adduct formation$$\ce{ArOCH3 + BBr3 -> ArO+(^{−}...

8

That reaction will definitely not yield a phenol. Phenols are not usually prepared directly from benzene, but from benzene derivatives, such as toluene or chlorobenzene: Oxidation of toluene, as developed by Dow Chemical: $\ce{C6H5CH3 + 2 O2 → C6H5OH + CO2 + H2O}$ Hydrolysis of chlorobenzene, using base or steam (Raschig–Hooker process): $\ce{C6H5Cl + ... 8 You have outlined that the formyl chloride is generated as the reactive, electrophilic intermediate under these conditions. You are planning to perform an electrophilic aromatic substitution, but in a phenol, there's high electron density on the$\ce{O}$atom. Isn't it conceivable that your main reaction product is phenylformate here, resulting from$\ce{O}$... 8 First of all we must have to note that the difference in reactivity between anisole (methoxybenzene) and phenol is small. Small enough for the undergraduate texts I own to not mention anisole separately from phenol, just referring to it as having "phenol-like reactivity" (i.e. strong ortho-para directing). We can more or less measure the difference in ortho-... 8 I want to make sure that you understand the different between two commonly confused molecules (their names don't help). Phenol is an$\ce{-OH}$group directly attached to an aromatic ring. Because of this connectivity, phenols exhibit different chemical behavior than other alcohols. In particular they are more acidic. Phenol can be abbreviated$\ce{PhOH}$, ... 8 According to the current version of Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013 (Blue Book), the retained names “aniline” and “phenol” are preferred IUPAC names (PINs). Parent structures having retained names are called functional parent compounds. For both retained names, substitution is permitted at any ... 8 Experimentally, the$\mathrm pK_\mathrm a$values for 3-chlorophenol and 3-fluorophenol appear to be (perhaps unexpectedly) equivalent. The table below1 shows the measured$\mathrm p K_\mathrm a$values of substituted phenols in dimethyl sulfoxide (DMSO):$$\begin{array}{ccc} \hline \text{substituent} & \sigma & \mathrm p K_\mathrm a \\ \hline \ce{... 7 The$\text{p}K_{\text{a}}$of ethanoic acid is$4.8$while the$\text{p}K_{\text{a}}$of phenol is$10$. So ethanoic acid is indead more acidic than phenol (for an explanation of$\text{p}K_{\text{a}}\$ values and their connection to acid strength see my answer here). And this is only to be expected from an intuitive point of view: one might say phenol is ...

7

O-protonated phenols direct in meta, according to an article on that topic. As it occurs, phenols can be, depending on acid, protonated on oxygen, but also on carbon, and even diprotonated (but not twice on the same atom), when most powerful mixtures of HF and SbF5 are used. O-protonated forms can be brominated, hydroxylated and alkilated. C-protonated forms ...

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