Questions tagged [carbonyl-compounds]

For questions about compounds containing the carbonyl group, C=O, the carboxylic acid group (-COOH), or its derivatives (anhydrides/esters/amides/acid halides). For questions about complexes involving carbon monoxide as a ligand use [carbonyl-complexes] instead.

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18
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1answer
12k views

Migratory aptitude in Baeyer-Villiger reaction

In short, I do not understand how or why the migratory aptitude is as listed in every textbook I've read. Firstly, they talk about a positive charge being built up that is stabilised by the movement ...
17
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4answers
22k views

Why is acetic acid more acidic than phenol?

Acetic acid (ethanoic acid, $\mathrm pK_\mathrm a \approx 5$) is more acidic than phenol ($\mathrm pK_\mathrm a \approx 10$), which is reflected in their reactivity with a weak base such as sodium ...
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3answers
47k views

Rationalising the order of reactivity of carbonyl compounds towards nucleophiles

This is immediately following ron's answer from Why is a ketone more nucleophilic than an ester? One of the most simplest questions you can ask, how can you rationalise the order of reactivity ...
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2answers
9k views

Comparing acidities of substituted and aromatic carboxylic acids

When comparing the acidities of carboxylic acids, we primarily see the electropositivity of the carboxylic acid carbons, i.e. we see how effectively the negative charge on the carboxylate ion is ...
9
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1answer
1k views

In what way could benzoin give Tollen's test?

In Q29 of Joint Entrance Exam (JEE) 2016 India, the official answer key mentions that benzoin gives Tollen's test. However, I saw this post which says that it doesn't: Why do α-hydroxy ketones give ...
21
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2answers
3k views

Does a Grignard reagent react with enones to give the 1,2- or 1,4- product?

Cyclohexenone, an α,β-unsaturated ketone, is electrophilic at both the carbonyl carbon, as well as the β-carbon. So, it can either undergo 1,2-addition to give the allylic alcohol 1, or 1,4-addition ...
19
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3answers
5k views

Which compound reacts faster in the Cannizzaro Reaction?

Which reacts faster in the Cannizzaro Reaction? a) $\ce{OHC-C6H4-NO2}$ b) $\ce{OHC-C6H4-OCH3}$ Obviously, a better hydride releasing group will react faster. Therefore my answer was b, as $\ce{-...
21
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4answers
5k views

Why do Organolithium or Grignard reagents act as nucleophiles and not as bases with aldehydes and ketones

I've read entire Chapter 14: Organometallic Compounds of Francis Carey's "Organic Chemistry" but I still didn't get an answer to my question. Quote from the book: Because of their basicity ...
15
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2answers
6k views

Is tropone aromatic?

Looking at resonance structure 1a, it doesn't seem that tropone is aromatic. However, the resonance structure 1b with $\ce{C+-O-}$ satisfies Hückel's rule for aromaticity. Is it correct to say that ...
4
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1answer
8k views

Mechanism for oxidation of primary alcohols to carboxylic acids

My teacher told me that the following is the mechanism for oxidation of primary alcohols to carboxylic acids: I've searched in books and online and didn't find a similar mechanism. For example, in ...
14
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2answers
30k views

Why does benzaldehyde not respond to Fehling's test?

All aldehydes are supposed to respond to Fehling's test. So why doesn't benzaldehyde respond to it? Does it have something to do with the fact that benzaldehyde is an aromatic compound? If so, then ...
4
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1answer
1k views

How can this ketone show Cannizzaro reaction?

According to answer key, Cannizzaro reaction of 3-hydroxy-2,2-dimethyl-1-phenylpropan-1-one (a ketone) takes place but how is that possible when we know only aldehydes show Cannizzaro reaction?
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1answer
446 views

Epoxide ring opening via decarboxylation

The answer for the above multiple choice problem is option (C), from which I can understand that at some point in the mechanism the molecule must've undergone decarboxylation. Also, I think the first ...
25
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1answer
881 views

How can I determine if there are π-π interactions between an amide and an aromatic ring in a protein?

In a crystal structure I've determined, a triazole ring on my ligand appears to be stacking with a tyrosine (top in picture): However, there is also an amide, courtesy a glutamine, near it (bottom). ...
15
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1answer
16k views

Reduction of carboxylic acids by LiAlH4

I've read that when a carboxylic acid reacts with $\ce{LiAlH4}$ the corresponding alcohol is formed: But when I try to think of the mechanism, I get stuck here: $\ce{LiAlH4}$ produces $\ce{H-}$. ...
9
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3answers
42k views

Mechanism for reaction of Tollens' reagent with aldehydes

Upon treatment with Tollens' reagent (ammoniacal silver(I) nitrate), aldehydes are oxidised to carboxylic acid, and silver(I) is reduced to silver metal. I am trying to find a mechanism for the this ...
14
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2answers
7k views

Can an amide nitrogen be a hydrogen bond acceptor?

Can $\ce{N}$ (i.e. main chain $\ce{NH}$s of recognised residues in a peptide or protein) be a hydrogen bond acceptor? It is a well known fact that the main chain $\ce{NH}$s can be a hydrogen bond ...
12
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2answers
2k views

How is the Felkin-Anh model of stereoinduction correctly explained with MO theory?

One method to predict stereoinduction in asymmetric reactions is the Felkin-Anh model (derived from the more basic Cram model) that applies to nucleophile attacks on α-chiral aldehydes. In a ...
12
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2answers
2k views

Regioselective enolate formation

Our professor only told us that A is favored, and B is not getting formed. I thought about the resonance structures and saw a contradiction to that what the prof told us. To be honest I think my ...
11
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1answer
44k views

What is the mechanism for oxidation of ketones by the Popoff's rule?

Ketones are relatively much harder to oxidise, but they do undergo oxidation reactions at extreme temperatures. Our teacher also told us about Popoff's rule which states that, on oxidation of ...
11
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1answer
4k views

Why do alpha-hydroxy ketones respond positively to Tollens', Fehling's, Benedict's, Schiff's and HgCl2 tests?

I learnt from a certain textbook that aldehydes and formic acid respond positively to Tollens', Fehling's, Benedict's, Schiff's and HgCl2 tests. However, in another textbook I read that even alpha-...
8
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1answer
2k views

Why are beta-ketoacids better at decarboxylation than gamma or delta?

My book claims that beta-ketoacids and beta-dicarboxylic acids are better at decarboxylating than their gamma and delta counterparts. Why is that? I would assume that since gamma and delta keto-acids ...
10
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2answers
12k views

Does acetic acid give a positive result with the iodoform test?

Acetic acid contains a $\ce{-COMe}$ group, so theoretically, it should give a positive result in the iodoform test (i.e. a yellow precipitate of $\ce{CHI3}$ being formed). But apparently the iodoform ...
3
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1answer
802 views

Triple Bond Character in Acyl Chlorides

I am told that because of the poor overlap between a chlorine atom and a carbon atom and chlorine's relatively high electronegativity, there is a strong partial positive character on the central ...
12
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1answer
18k views

Mechanism of carboxylic acid and amide dehydration with phosphorus pentoxide

Dehydration of carboxylic acids with phosphorus pentoxide ($\ce{P2O5}$) yields acid anhydrides, and in a similar reaction, amides dehydrated with phosphorus pentoxide yield cyanides. Can an arrow ...
6
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2answers
4k views

Cannizarro reaction of chloral

When chloral undergoes reaction with a concentrated alkali, will it undergo Cannizarro reaction to form the corresponding alcohol and acidic salt, or should it form chloroform instead by departure of ...
6
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1answer
12k views

IUPAC name for citric acid

I wonder what the name is of the following structure is: I think it's something like 3-hyrodxypentanoic diacid However, I wasn't able to find how to name a side chain if it contains a $\ce{COOH}$ ...
6
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1answer
2k views

Are groups other than carbonyl reduced by Clemmensen reduction?

According to my textbook, Clemmensen reduction reduces only aldehydes and ketones to alkanes. But in this question: $\ce{Zn-Hg/HCl}$ has reduced both the ketonic and nitro group. Correct answer given ...
2
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1answer
3k views

Dehydration of amide with PCl5

Can $\ce{PCl5}$, phosphorus pentachloride, react with an amide? I saw a reaction where the corresponding cyanide was formed in this process. What other reagents could do the same?
7
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4answers
917 views

Do enolates get protonated at the carbon or oxygen atom?

An enolate has two resonance structures. When it gets protonated, where is the $\ce{H+}$ more likely to go? On the oxygen to produce an enol, which tautomerizes to the keto, or on directly onto the ...
6
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1answer
1k views

Can the hydroxyl group of 4-hydroxybenzoic acid react with phosphorus pentachloride?

I learned that, a phenol will not react (or react very slowly) with $\ce{PCl5}$ due to its stabilized structure. How about the $\ce{-OH}$ group on the benzene ring of 4-hydroxybenzoic acid? Will that ...
6
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2answers
12k views

Does Br2/H2O oxidize all aldehydes?

In many books, it is mentioned that aldehydes are easily oxidized even by mild oxidizing agents. However, I have never seen bromine water explicitly mentioned. But in the carbohydrates chapter, it is ...
5
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3answers
929 views

Which tautomer of hexane-2,4-dione is more stable?

Which tautomer will be more stable? Both 1 and 2 show intramolecular hydrogen bonding and form 6 membered cyclic ring, thus increasing the stability. I think I need to compare the effect of the two ...
3
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2answers
624 views

Which is the correct way to name pentan-3-one?

I have seen this organic compound named in two different ways. According to some sources it is written pentan-3-one.. Other sources call it 3-pentanone. Which one is correct?
0
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1answer
744 views

Why does a hydride shift take place in the cannizzaro reaction?

Hydride is a poor leaving group so a hydride shift should not take place and instead the attacking hydroxyl should leave the carbonyl group. I don’t understand why this doesn’t happen?
18
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2answers
859 views

Mechanism of a dephenylation reaction

I recently came across this reaction in my undergraduate labs. The experiment is taken from this article: J. Chem. Educ., 2008, 85, 413. The condensation of 2-methoxynaphthalene with cinnamoyl ...
9
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2answers
48k views

Why doesn't the Brady's test (2,4-DNPH) work on carboxylic acids?

Why does the Brady's test, the reaction of 2,4-dinitrophenylhydrazine with aldehydes and ketones, fail with carboxylic acids?
7
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2answers
12k views

Which will be the most acidic hydrogen in the following organic compounds?

Which will be the most acidic hydrogen in both cases? Please explain. According to me, in the first compound 2 should be most acidic as in both 1 and 2, resonance occurs but 2’s carbon is closer to ...
4
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1answer
3k views

Is propane-1,2,3-tricarbaldehyde the correct IUPAC name of CHO-CH2-CH(CHO)-CH2-CHO?

We were asked this question in class: What is the IUPAC name of the compound $\ce{CHO-CH2-CH(CHO)-CH2-CHO}?$ I don't know for sure, but I think the answer should either be 3-formylpentan-1,5-dial ...
2
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1answer
18k views

How does sodium in ethanol reduce carbonyl compounds?

According to my teacher, Na in ethanol reduces carbonyl compounds (e.g. aldehydes and ketones) to alcohols. However, I can't see where the hydrogen needed for reduction comes from. How does the ...
14
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1answer
2k views

Mechanism for basic hydrolysis of α-chloronitrile to ketone?

In Corey's 1969 prostaglandin synthesis,1 compound 2 is formed from compound 1 by: [...] treatment with 2.5 equiv of potassium hydroxide (added as a hot saturated aqueous solution) in dimethyl ...
4
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3answers
4k views

Is there intramolecular hydrogen bonding in salicylaldehyde?

Is there intramolecular hydrogen bonding between the hydroxyl and carbonyl groups? I think personally is that it does but what is concerning me is that I have got no adequate answer or response to my ...
3
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1answer
2k views

Carbonyl oxygen as nucleophile

Aldehydes and ketones have electrophilic centres at their carbonyl C, since the carbonyl O polarises the bond and attracts electron density towards itself on account of its high electronegativity. But ...
12
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2answers
14k views

Why is a ketone more nucleophilic than an ester?

I guess the ester is a weaker nucleophile because it does have an additional oxygen atom, unlike the ketone, that is pulling electrons from the C-O double bond towards the carbon atom (this happens ...
9
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1answer
9k views

Why does LiAlH4 reduce an amide to an amine, but only reduce a ketone/aldehyde to an alcohol?

Here are two different reactions in which lithium aluminium hydride, $\ce{LiAlH4}$, reduces a carbonyl group: Why does $\ce{LiAlH4}$ completely remove the oxygen from the amide, but only reduces the ...
9
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1answer
4k views

Decarboxylation of Salicylic acid

I would like to know how and under what conditions can decarboxylation of salicylic acid (o-hydroxybenzoic acid) occur. I couldn't find any sources for it online. Here are some reasons I think it ...
8
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3answers
591 views

Does the synthesis of beta-keto phosphonates from esters have a name?

Consider the Horner–Wadsworth–Emmons reaction; one of its reactants is a phosphonate, usually stabilised by a β-carbonyl group which is then deprotonated in α position (figure 1). These ...
8
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2answers
1k views

How can an aromatic ketone be reduced in the presence of a nitro group?

Is it possible to reduce an acyl group to an alkane, but still keep a nitro group intact without its reduction to an amino group? A Clemmensen reduction would reduce the nitro group, and it seems like ...
7
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2answers
788 views

Why does formaldehyde exist primarily as the gem-diol in aqueous solution?

From Wikipedia, Methanediol is the product of the hydration of formaldehyde $\ce{H2C=O}$, and predominates in water solution: the equilibrium constant being about $10^3$ and in a 5% by weight ...
7
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3answers
14k views

Why amino acids (Zwitterion) become either negative or positive at low and high pH solutions?

The amino acids are Zwitterions. In neutral pH, an Amino acid's amino group has a postive charge and Carboxyl group has negative charge. They cancel each others charge thanks to the $Hydrogen$ that's ...