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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25
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3answers
48k 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 ...
25
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1answer
942 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). ...
22
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2answers
4k 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 ...
21
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4answers
6k 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 ...
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{-...
18
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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 ...
18
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2answers
952 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 ...
18
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4answers
24k 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 ...
18
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1answer
13k 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 ...
16
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1answer
9k views

Why do BH3 and NaBH4 have different selectivities?

I've always known borane ($\ce{BH3}$), as a reagent for alkene hydroboration. Recently in class we talked about its use in the reduction of carboxylic acids to alcohols as well. Now obviously $\ce{...
15
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2answers
32k 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 ...
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 ...
15
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1answer
612 views

ICHO Synthesis Problem 2018

I've several doubts about this ICHO synthesis problem, which was a part of the preparatory problem package of 2018 (so yes, it's not a part of an ongoing contest) Before sharing the answer given, I'...
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 $\ce{H-}$. ...
14
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2answers
7k views

Why does the carbonyl group in an acid anhydride have two stretching frequencies?

The carbonyl stretching frequencies for an acid anhydride are approximately $1820~\mathrm{cm^{-1}}$ and $1760~\mathrm{cm^{-1}}$. These are both higher frequencies than a simple ketone owing to the ...
14
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1answer
1k views

Clarifications about the mechanism of the Wittig reaction [closed]

Ok so this is the proposed mechanism for the Wittig Reaction as stated by my textbook, LG Wade. I have some doubts regarding this mechanism: 1) Why is only triphenyl phosphine used here? Why not ...
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 ...
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 ...
14
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1answer
872 views

How can benzaldehyde have a pKa of 14.9?

There are numerous websites out there which claim that the pKa of benzaldehyde – C6H5CHO – is 14.90. (Just do a Google search for benzaldehyde pka to see what I ...
14
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1answer
4k views

Synthesis of mandelic acid from benzaldehyde

For an upcoming exam, I have to describe the synthesis of 2-hydroxy-2-phenylacetic acid (mandelic acid) from benzaldehyde. The provided answers describe quite a long process, consisting of 8 stages. ...
13
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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 ...
12
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4answers
2k views

What's the mechanism of the reaction of (E)-methyl 3-(furan-2-yl)acrylate in acidic methanol?

In the organic chemistry textbook by Clayden et al. they mention that the reaction of (E)-methyl 3-(furan-2-yl)acrylate in acidic methanol yields dimethyl 4-oxoheptanedioate without providing the ...
12
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3answers
52k views

Why are the boiling points of aldehydes less than those of ketones?

Both aldehydes and ketones have a carbonyl group, but since the carbonyl group of ketone is between alkyl groups, wouldn't it be more difficult for it to form hydrogen bonds than aldehydes? Why then, ...
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 ...
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 ...
12
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4answers
7k views

Is it possible to synthesise ethers from carboxylic acids?

Is it possible to synthesise ethers from carboxylic acids, and if so, how? By ether I mean an ether in general ($\ce{R-O-R'}$), not just specific examples. I theorised one could perform Fischer ...
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
votes
1answer
248 views

How do I synthesize 3-phenyloxirane-2-carbaldehyde from chloroacetonitrile?

How do I synthesize 3-phenyloxirane-2-carbaldehyde from chloroacetonitrile? My proposed route involves: hydrolysis of the nitrile to form a carboxylic acid, and subsequent esterification then, a ...
12
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1answer
386 views

Single electron reduction of ketone by Na or Zn

Whenever we add Na or Zn metal to a ketone, why does the electron prefer to attack the carbonyl bond and form a radical, instead of removing the acidic hydrogen and forming an enolate and $\ce{H2}$ ...
11
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4answers
2k views

Reasons for negative iodoform test

Why does 2',6'-dimethylacetophenone not give iodoform test?
11
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1answer
46k 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
16k views

Is an ester or a ketone more acidic?

Two organic chemistry textbooks I've read (by Bruice and by Tandon) say: Esters are more acidic than ketones, because the resonance between the two oxygen atoms gives less opportunity for the ...
11
votes
1answer
210 views

Mechanism of radical cyclisation to form hydroazulene core

Recent studies on radical-induced cyclisation reactions have led to a simple, one-step method for the preparation of hydroazulenes from appropriately substituted cyclopentanone precursors. Treatment ...
11
votes
2answers
555 views

Which is the most acidic proton of (3Z)-3-ethylidenecyclopent-1-ene-1-carbaldehyde?

At first glance, I thought the most acidic protons would be the ones in red due to their proximity to the carbonyl. However, the answer key has the hydrogens in green as the most acidic. Can someone ...
11
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5answers
3k views

Why can enolizable aldehydes undergo Cannizzaro reactions?

Why does 2-methylpropanal undergo a Cannizzaro reaction even though it has an $\alpha$-hydrogen?
11
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1answer
963 views

In the Favorskii rearrangement, why doesn't the base grab the alpha hydrogen of the carbon bearing the halogen?

In the Favorskii rearrangement, the base (like hydroxide) always abstracts the alpha hydrogen of the carbon not bearing the halogen. But to me the hydrogens on the carbon directly connected to the ...
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-...
10
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2answers
1k views

Prediction of products in reaction of dicarbonyl with alpha-haloketone

Following is the question that was asked in my exam. a,b,c,d are the various options, one of which is the answer. I am familiar with the Reformatsky reaction, Aldol condensation, Knoevenagel's ...
10
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2answers
2k views

Rearrangements of α-aminoketones in Clemmensen reduction

What is the possible mechanism for this reaction? Activated zinc in presence of concentrated hydrochloric acid is used for Clemmensen reduction, that is conversion of ketone group to methylene group. ...
10
votes
1answer
609 views

What is the significance of the 2 and 4 positions in 2,4-DNP?

2,4-dinitrophenylhydrazine, a popular laboratory reagent is used to identify carbonyl compounds by forming 2,4-dinitrophenylhydrazones, which are often red or yellow colored precipitates. Why is the ...
10
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2answers
6k views

What are the products of the reaction of 1-methoxycyclohexene with dilute hydrochloric acid?

When 1-methoxycyclohexene is treated with dilute aqueous hydrochloric acid, methanol is produced along with another organic product. Identify this product. Explain why methoxycyclohexane is inert ...
10
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1answer
235 views

Why is nitrosobenzene electrophilic on O in organocatalytic oxygenations?

In 2003 Zhong1 and MacMillan2 reported the use of nitrosobenzene, PhNO, in the organocatalytic asymmetric α-oxygenation of carbonyl compounds: which is all nice, except for the slightly ...
10
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1answer
282 views

Esterfication of 2,2,2-triphenylethanoic acid

Explain the formation of (1,1,1-triphenylmethyl)methyl ether when a solution of 2,2,2-triphenylethanoic acid in concentrated sulfuric acid is poured in methanol. I cannot figure out where is one ...
10
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1answer
745 views

Enolate formation and tosylate displacement in cis/trans decalin

What will happen in the following reactions? This is Problem 3d from Chapter 6 of Zweifel and Nantz's Modern Organic Synthesis. I thought that after the hydroxyl group is converted into a good ...
10
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4answers
698 views

With which group does the middle oxygen atom of an anhydride remain, on hydrolysis?

With which group does the middle oxygen atom of an anhydride remain, on hydrolysis? As an example, let us say we have the following modification of ethanoic methanoic anhydride, with the middle oxygen ...
10
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1answer
282 views

Protonating/basic site and Brønsted basicity orders of beta, gamma, and delta lactams

Consider the three cyclic amides: $\beta$-lactam $\gamma$-lactam $\delta$-lactam My question What is the basic site (site of protonation) for these three lactams? And what should be their Brønsted ...
10
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2answers
13k 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 ...
9
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3answers
4k views

Is sodium borohydride really a better base than an alcohol?

I have learnt that sodium borohydride can reduce aldehydes, ketones and acyl chlorides into alcohols. However, it fails to react with esters or acid anhydrides. On the other hand, alcohols — ...
9
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2answers
1k views

Nomenclature of a cyclic ketone

Why isn't this molecule named 2-fluorocyclopent-1-one?
9
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3answers
46k 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 ...