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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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 ...
Jeevesh Juneja's user avatar
29 votes
2 answers
15k 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 ...
miyagi_do's user avatar
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28 votes
3 answers
60k 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 ...
Martin - マーチン's user avatar
28 votes
3 answers
11k 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{-...
Shubham's user avatar
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27 votes
2 answers
52k 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 ...
user avatar
26 votes
4 answers
44k 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 ...
Manisha Poudel's user avatar
25 votes
1 answer
2k 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). ...
Nick T's user avatar
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24 votes
2 answers
10k 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 ...
stochastic13's user avatar
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22 votes
4 answers
8k 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 ...
claws's user avatar
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22 votes
1 answer
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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 ...
Ari Ben Canaan's user avatar
21 votes
1 answer
21k views

Can hydrogen on platinum reduce carboxylic acids and esters?

Can $\ce{H2/Pt}$ reduce carboxylic acids and esters? I am confused about the reducing nature of hydrogen in presence of platinum. In some books, it reduces carboxylic acid and ester while in others, ...
Arvind Tiwari's user avatar
21 votes
1 answer
29k 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 $\ce{H-}$. ...
Quark's user avatar
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21 votes
1 answer
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Can we use phosphorus triiodide in Hell-Volhard-Zelinsky reaction?

Using the Hell–Volhard—Zelinksy (HVZ) reaction, we can get alpha-chloro or alpha-bromo carboxylic acids: Is it possible to similarly make alpha-iodo carboxylic acids with the help of HVZ reaction? I ...
Nilay Ghosh's user avatar
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20 votes
1 answer
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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'...
stoic-santiago's user avatar
19 votes
1 answer
25k views

Does Br2/H2O oxidize all aldehydes including carbohydrates?

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 ...
Kartik's user avatar
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19 votes
2 answers
2k 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 ...
orthocresol's user avatar
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19 votes
3 answers
79k 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, ...
Rajath Radhakrishnan's user avatar
19 votes
1 answer
4k 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 ...
orthocresol's user avatar
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19 votes
1 answer
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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 ...
Akash Goel's user avatar
18 votes
2 answers
25k 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 ...
Jori's user avatar
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17 votes
1 answer
57k 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 ...
nilanjana's user avatar
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17 votes
1 answer
22k 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{...
Anne's user avatar
  • 417
17 votes
2 answers
14k 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 ...
EJC's user avatar
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17 votes
1 answer
22k 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 ...
rishab bairagi's user avatar
17 votes
1 answer
21k views

Which factors determine the keto:enol ratio for aldehydes, ketones, and 1,3-dicarbonyl compounds?

Arrange the following compounds in order of increasing enol content: I think the order is D > C > B > A considering conjugation, hyperconjugation and hydrogen bonding. The enol formed in ...
Aditya Dev's user avatar
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16 votes
4 answers
5k views

Reasons for negative iodoform test

Why does 2',6'-dimethylacetophenone not give iodoform test?
lowkeyy's user avatar
  • 313
16 votes
1 answer
12k 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 ...
mkHun's user avatar
  • 213
16 votes
1 answer
7k views

Why is enol content higher in non-polar solvents?

Apparently, for keto-enol tautomerism, the enol content of a given carbonyl compound increases when in a non-polar solvent. What is the reason for this?
Pranjal Mittal's user avatar
15 votes
5 answers
7k views

Why can enolizable aldehydes undergo Cannizzaro reactions?

Why does 2-methylpropanal undergo a Cannizzaro reaction even though it has an $\alpha$-hydrogen?
Utkarsh Gupta's user avatar
15 votes
2 answers
4k 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. ...
stoic-santiago's user avatar
15 votes
1 answer
20k 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 ...
mshum's user avatar
  • 305
15 votes
1 answer
3k 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 ...
Saba Tavdgiridze's user avatar
15 votes
1 answer
25k 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 ...
Charles's user avatar
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15 votes
1 answer
6k 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. ...
avramov's user avatar
  • 335
15 votes
2 answers
6k views

Reaction of glucose with 2,4-dinitrophenylhydrazine (DNPH)

In its open-chain form, glucose possesses an aldehyde group; however, glucose does not test positive with 2,4-dinitrophenylhydrazine (which typically forms a yellow/orange/red precipitate with ...
Manish Bhatt's user avatar
14 votes
4 answers
4k 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 ...
Philipp's user avatar
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14 votes
2 answers
68k 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?
user58953's user avatar
  • 497
14 votes
2 answers
12k 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 ...
RobChem's user avatar
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14 votes
1 answer
2k 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 ...
user avatar
14 votes
1 answer
824 views

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

(2,4-Dinitrophenyl)hydrazine, 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 ...
Pritt says Reinstate Monica's user avatar
14 votes
1 answer
60k views

How do you identify reducing / non-reducing sugar by looking at structure?

Identifying reducing / non-reducing sugar been confusing me for a while now , I know that reducing sugar contain aldehyde or ketone group . It's easy to identify them in monosaccharides but this ...
Heisenberg's user avatar
14 votes
1 answer
1k views

Ambiguous nature of aldehydic group in glucose

In aqueous solution, α-anomer and β-anomer of glucose remain in equilibrium with each other along with a small amount of glucose in open chain form ($0.02~\%$). The open chain form in ...
Yashas's user avatar
  • 2,096
14 votes
4 answers
6k views

How to predict the outcome of a crossed Cannizzaro reaction?

My question is, how do we predict the products of a cross-Cannizzaro disproportionation in presence of a concentrated base? i.e, How to judge which of the aldehydes (both don't have any alpha hydrogen)...
Saurabh Raje's user avatar
14 votes
2 answers
3k 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 ...
Jan's user avatar
  • 68k
13 votes
1 answer
1k views

Does folic acid contain a benzyl or a phenyl group?

I'm studying for my MCAT currently and I stumbled upon this question. It gives the structure of a folic acid molecule and asks what functional groups can be found within the molecule. I understand ...
Zaid Nour's user avatar
  • 139
13 votes
1 answer
8k views

Does an acetal give a positive Tollens test?

In Organic Chemistry (Wade) there is a question: Which of the following compounds would give a positive Tollens' test? (Remember that the Tollens' test involves mild basic aqueous conditions.) The ...
user4779's user avatar
  • 691
13 votes
2 answers
6k views

Why is benzoic acid a stronger acid than 3-aminobenzoic acid?

Why is benzoic acid a stronger acid than 3-aminobenzoic acid? Obviously at meta position, only negative inductive effect will operate. But, how does that make it a weaker acid than benzoic acid?
Prajwal Chauhan's user avatar
13 votes
1 answer
647 views

Unusual hydrolysis of methyl 2,4,6‐trimethylbenzoate

Problem 223 from Conceptual Problems in Organic Chemsitry by Singh [1, p. 367]: The given answer is b and I don't get why. Usual ester hydrolysis would've given a. I somehow managed to know that the ...
user avatar
13 votes
1 answer
1k views

What is the most acidic proton of 2-methylcyclopent-2-en-1-one?

In an acid-base reaction of $\ce{HO-}$ with 2-methylcyclopent-2-en-1-one, which is the most acidic proton? I had assumed it was one of them coming off C-5 according to IUPAC numbering (the sp3 carbon ...
vitno's user avatar
  • 133
13 votes
3 answers
502 views

Comparison of C=O bond strength in metal carbonyls

Find the weakest $\ce{C=O}$ bond among $\ce{[Mn(CO)6]+},$ $\ce{Fe[(CO)5]},$ $\ce{[Cr(CO)6]}$ and $\ce{[V(CO)6]-}.$ I thought the $\ce{C=O}$ bond strength would be lowest in $\ce{[V(CO)6]-}$ since the ...
m-Xylene's user avatar
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