Can a cyclic amine form an amide?Is pyrene aromatic despite failing Hückel's rule?What is Y-aromaticity? Is the trinitromethanide anion aromatic?Do lone pairs on substituents (e.g. in aniline) count towards Hückel's rule?What is the justification for Hückel's rule?Applying Huckel's rule to non-planar compoundsHydrolysis of cyanohydrinAttack of amine on amideHofmann Elimination with a Cyclic AmineMechanism for formation of amide by reaction of amine with esterWhat test can be used to differ amide and amine?Evaluation of a synthesis from aspirin to paracetamol from YouTubeAmine and Amide reactions with ketoneWhich of these functional groups is soluble in aqueous HCl and/or NaOH?What is the balanced equation of BH3/THF with an amide to form an amine?Can amide bonds fragment in ESI-MS?
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Can a cyclic amine form an amide?
Is pyrene aromatic despite failing Hückel's rule?What is Y-aromaticity? Is the trinitromethanide anion aromatic?Do lone pairs on substituents (e.g. in aniline) count towards Hückel's rule?What is the justification for Hückel's rule?Applying Huckel's rule to non-planar compoundsHydrolysis of cyanohydrinAttack of amine on amideHofmann Elimination with a Cyclic AmineMechanism for formation of amide by reaction of amine with esterWhat test can be used to differ amide and amine?Evaluation of a synthesis from aspirin to paracetamol from YouTubeAmine and Amide reactions with ketoneWhich of these functional groups is soluble in aqueous HCl and/or NaOH?What is the balanced equation of BH3/THF with an amide to form an amine?Can amide bonds fragment in ESI-MS?
$begingroup$
This is a question from the Cambridge International Examinations October/November 2017 (pdf from papers.gceguide.com, pdf via the Wayback Machine).
I need to understand why the secondary amine in the serotonin molecule does not undergo condensation reaction with $ceCH3COCl$.
Because, as far as I know, there should be an amide formation for this reaction.
Here's a picture of serotonin:
I must be lacking some information making that $ceNH$ unsuitable for this reaction. And I know that the other amine and the phenol reacts with $ceCH3COCl$.
organic-chemistry amines amides
edited Apr 30 at 12:46
Martin - マーチン♦
34.1k9112240
asked Apr 29 at 9:06
Amar30657Amar30657
896
$endgroup$
|
show 2 more comments
$begingroup$
This is a question from the Cambridge International Examinations October/November 2017 (pdf from papers.gceguide.com, pdf via the Wayback Machine).
I need to understand why the secondary amine in the serotonin molecule does not undergo condensation reaction with $ceCH3COCl$.
Because, as far as I know, there should be an amide formation for this reaction.
Here's a picture of serotonin:
I must be lacking some information making that $ceNH$ unsuitable for this reaction. And I know that the other amine and the phenol reacts with $ceCH3COCl$.
organic-chemistry amines amides
edited Apr 30 at 12:46
Martin - マーチン♦
34.1k9112240
asked Apr 29 at 9:06
Amar30657Amar30657
896
$endgroup$
$begingroup$
Secondary amine group shown here is quite sterically hindered..Approach at Burgi-Dunitz trajectory would most probably be difficult
$endgroup$
– YUSUF HASAN
Apr 29 at 9:16
$begingroup$
Did you mean lone pair of electron in N is less available for carbocation to be attacked? @YUSUFHASAN
$endgroup$
– Amar30657
Apr 29 at 9:27
$begingroup$
No..I mean what you have in mind is a nucleophilic attack by NH on CH3COCl as the first step, right? So that would be retarded by steric hindrance..
$endgroup$
– YUSUF HASAN
Apr 29 at 9:29
4
$begingroup$
Nothing to do with sterics. The lone pair on the nitrogen is delocalised into the aromatic system so is not available for nucleophilic attack. If you want to functionalise the indole-NH you generally have to formally deprotonate with strong base. Otherwise it reacts as an enamine through the 3-position.
$endgroup$
– Waylander
Apr 29 at 9:53
1
$begingroup$
@Amar30657 You need to read more about aromatic systems. en.wikipedia.org/wiki/Indole
$endgroup$
– Waylander
Apr 29 at 10:05
|
show 2 more comments
$begingroup$
This is a question from the Cambridge International Examinations October/November 2017 (pdf from papers.gceguide.com, pdf via the Wayback Machine).
I need to understand why the secondary amine in the serotonin molecule does not undergo condensation reaction with $ceCH3COCl$.
Because, as far as I know, there should be an amide formation for this reaction.
Here's a picture of serotonin:
I must be lacking some information making that $ceNH$ unsuitable for this reaction. And I know that the other amine and the phenol reacts with $ceCH3COCl$.
organic-chemistry amines amides
edited Apr 30 at 12:46
Martin - マーチン♦
34.1k9112240
asked Apr 29 at 9:06
Amar30657Amar30657
896
$endgroup$
This is a question from the Cambridge International Examinations October/November 2017 (pdf from papers.gceguide.com, pdf via the Wayback Machine).
I need to understand why the secondary amine in the serotonin molecule does not undergo condensation reaction with $ceCH3COCl$.
Because, as far as I know, there should be an amide formation for this reaction.
Here's a picture of serotonin:
I must be lacking some information making that $ceNH$ unsuitable for this reaction. And I know that the other amine and the phenol reacts with $ceCH3COCl$.
organic-chemistry amines amides
organic-chemistry amines amides
edited Apr 30 at 12:46
Martin - マーチン♦
34.1k9112240
asked Apr 29 at 9:06
Amar30657Amar30657
896
edited Apr 30 at 12:46
Martin - マーチン♦
34.1k9112240
asked Apr 29 at 9:06
Amar30657Amar30657
896
edited Apr 30 at 12:46
Martin - マーチン♦
34.1k9112240
edited Apr 30 at 12:46
Martin - マーチン♦
34.1k9112240
edited Apr 30 at 12:46
Martin - マーチン♦
34.1k9112240
34.1k9112240
asked Apr 29 at 9:06
Amar30657Amar30657
896
asked Apr 29 at 9:06
Amar30657Amar30657
896
asked Apr 29 at 9:06
Amar30657Amar30657
896
896
$begingroup$
Secondary amine group shown here is quite sterically hindered..Approach at Burgi-Dunitz trajectory would most probably be difficult
$endgroup$
– YUSUF HASAN
Apr 29 at 9:16
$begingroup$
Did you mean lone pair of electron in N is less available for carbocation to be attacked? @YUSUFHASAN
$endgroup$
– Amar30657
Apr 29 at 9:27
$begingroup$
No..I mean what you have in mind is a nucleophilic attack by NH on CH3COCl as the first step, right? So that would be retarded by steric hindrance..
$endgroup$
– YUSUF HASAN
Apr 29 at 9:29
4
$begingroup$
Nothing to do with sterics. The lone pair on the nitrogen is delocalised into the aromatic system so is not available for nucleophilic attack. If you want to functionalise the indole-NH you generally have to formally deprotonate with strong base. Otherwise it reacts as an enamine through the 3-position.
$endgroup$
– Waylander
Apr 29 at 9:53
1
$begingroup$
@Amar30657 You need to read more about aromatic systems. en.wikipedia.org/wiki/Indole
$endgroup$
– Waylander
Apr 29 at 10:05
|
show 2 more comments
$begingroup$
Secondary amine group shown here is quite sterically hindered..Approach at Burgi-Dunitz trajectory would most probably be difficult
$endgroup$
– YUSUF HASAN
Apr 29 at 9:16
$begingroup$
Did you mean lone pair of electron in N is less available for carbocation to be attacked? @YUSUFHASAN
$endgroup$
– Amar30657
Apr 29 at 9:27
$begingroup$
No..I mean what you have in mind is a nucleophilic attack by NH on CH3COCl as the first step, right? So that would be retarded by steric hindrance..
$endgroup$
– YUSUF HASAN
Apr 29 at 9:29
4
$begingroup$
Nothing to do with sterics. The lone pair on the nitrogen is delocalised into the aromatic system so is not available for nucleophilic attack. If you want to functionalise the indole-NH you generally have to formally deprotonate with strong base. Otherwise it reacts as an enamine through the 3-position.
$endgroup$
– Waylander
Apr 29 at 9:53
1
$begingroup$
@Amar30657 You need to read more about aromatic systems. en.wikipedia.org/wiki/Indole
$endgroup$
– Waylander
Apr 29 at 10:05
$begingroup$
Secondary amine group shown here is quite sterically hindered..Approach at Burgi-Dunitz trajectory would most probably be difficult
$endgroup$
– YUSUF HASAN
Apr 29 at 9:16
$begingroup$
Secondary amine group shown here is quite sterically hindered..Approach at Burgi-Dunitz trajectory would most probably be difficult
$endgroup$
– YUSUF HASAN
Apr 29 at 9:16
$begingroup$
Did you mean lone pair of electron in N is less available for carbocation to be attacked? @YUSUFHASAN
$endgroup$
– Amar30657
Apr 29 at 9:27
$begingroup$
Did you mean lone pair of electron in N is less available for carbocation to be attacked? @YUSUFHASAN
$endgroup$
– Amar30657
Apr 29 at 9:27
$begingroup$
No..I mean what you have in mind is a nucleophilic attack by NH on CH3COCl as the first step, right? So that would be retarded by steric hindrance..
$endgroup$
– YUSUF HASAN
Apr 29 at 9:29
$begingroup$
No..I mean what you have in mind is a nucleophilic attack by NH on CH3COCl as the first step, right? So that would be retarded by steric hindrance..
$endgroup$
– YUSUF HASAN
Apr 29 at 9:29
4
4
$begingroup$
Nothing to do with sterics. The lone pair on the nitrogen is delocalised into the aromatic system so is not available for nucleophilic attack. If you want to functionalise the indole-NH you generally have to formally deprotonate with strong base. Otherwise it reacts as an enamine through the 3-position.
$endgroup$
– Waylander
Apr 29 at 9:53
$begingroup$
Nothing to do with sterics. The lone pair on the nitrogen is delocalised into the aromatic system so is not available for nucleophilic attack. If you want to functionalise the indole-NH you generally have to formally deprotonate with strong base. Otherwise it reacts as an enamine through the 3-position.
$endgroup$
– Waylander
Apr 29 at 9:53
1
1
$begingroup$
@Amar30657 You need to read more about aromatic systems. en.wikipedia.org/wiki/Indole
$endgroup$
– Waylander
Apr 29 at 10:05
$begingroup$
@Amar30657 You need to read more about aromatic systems. en.wikipedia.org/wiki/Indole
$endgroup$
– Waylander
Apr 29 at 10:05
|
show 2 more comments
2 Answers
2
active
oldest
votes
$begingroup$
The heterocycle in this question is indole and is aromatic. This means that the N lone pair is delocalised and not readily available for nucleophilic attack. Think of it as similar in reactivity to a secondary amide nitrogen RCONHR. Generally you need to formally deprotonate to functionalise, though there are some interesting techniques using carbonyl azoles catalysed by DBU[1] and others using aldehyde and alcohol substrates.[2] Note that 3-unsubstituted indoles react with acyl halides by F-C acylation at the 3 position.[3]
References:
- Heller, S. T.; Schultz, E. E.; Sarpong, R. Chemoselective N-Acylation of Indoles and Oxazolidinones with Carbonylazoles. Angew. Chem. Int. Ed. 2012, 51 (33), 8304–8308 DOI: 10.1002/anie.201203976.
- Maki, B. E.; Scheidt, K. A. Single-Flask Synthesis ofN-Acylated Indoles by Catalytic Dehydrogenative Coupling with Primary Alcohols. Org. Lett. 2009, 11 (7), 1651–1654 DOI: 10.1021/ol900306v. PMID: 19320508 (with free text available).
- Okauchi, T.; Itonaga, M.; Minami, T.; Owa, T.; Kitoh, K.; Yoshino, H. A General Method for Acylation of Indoles at the 3-Position with Acyl Chlorides in the Presence of Dialkylaluminum Chloride. Org. Lett. 2000, 2 (10), 1485–1487 DOI: 10.1021/ol005841p.
edited Apr 30 at 12:40
Martin - マーチン♦
34.1k9112240
answered Apr 29 at 11:57
WaylanderWaylander
7,36911726
$endgroup$
add a comment |
$begingroup$
If you consider the lone pair on that N-atom and apply Hückel's (4n+2)π-e rule to check aromaticity , it satisfies all the conditions. So in order to achieve aromatic-stabilisation the nitrogen's valency is no more available for condensation!
answered Apr 29 at 13:41
ANBENZENEANBENZENE
1436
$endgroup$
$begingroup$
Hückel's rules should not be applied to this compound for two facts: 1. It is not a mono-cycle. 2. It is a heterocycle. It would be by far superior, at a more fundamental level, and even simpler to just state that the lone pair is delocalised. One could even show this with resonance structures, but that might be overkill.
$endgroup$
– Martin - マーチン♦
Apr 30 at 12:51
$begingroup$
Why can't we apply Hückel's rule? I didn't know that; would you please elaborate?
$endgroup$
– ANBENZENE
Apr 30 at 13:39
$begingroup$
Related: Is pyrene aromatic despite failing Hückel's rule? Do lone pairs on substituents (e.g. in aniline) count towards Hückel's rule? What is the justification for Hückel's rule? Applying Huckel's rule to non-planar compounds My answer covers it also: What is Y-aromaticity? Is the trinitromethanide anion aromatic?
$endgroup$
– Martin - マーチン♦
Apr 30 at 13:58
1
$begingroup$
Tl;dr: there are three criteria for which the rule has been observed. 1. monocyclic planar, 2. trigonal/diagonal hybridised atoms 3. (4n+2) pi electrons, n should not exceed 5. The calculations were done for $ce(CH)_m$, so they strictly only hold for these compounds. The third criteria has been used so often (and most of the times wrong) and is incredibly popular (also wrong), that it is perceived as Hückel's rule (also wrong). It is painful to see that it is taught like this, without teaching the underlying theory, which is possibly simpler than learning about the exceptions.
$endgroup$
– Martin - マーチン♦
Apr 30 at 14:05
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
The heterocycle in this question is indole and is aromatic. This means that the N lone pair is delocalised and not readily available for nucleophilic attack. Think of it as similar in reactivity to a secondary amide nitrogen RCONHR. Generally you need to formally deprotonate to functionalise, though there are some interesting techniques using carbonyl azoles catalysed by DBU[1] and others using aldehyde and alcohol substrates.[2] Note that 3-unsubstituted indoles react with acyl halides by F-C acylation at the 3 position.[3]
References:
- Heller, S. T.; Schultz, E. E.; Sarpong, R. Chemoselective N-Acylation of Indoles and Oxazolidinones with Carbonylazoles. Angew. Chem. Int. Ed. 2012, 51 (33), 8304–8308 DOI: 10.1002/anie.201203976.
- Maki, B. E.; Scheidt, K. A. Single-Flask Synthesis ofN-Acylated Indoles by Catalytic Dehydrogenative Coupling with Primary Alcohols. Org. Lett. 2009, 11 (7), 1651–1654 DOI: 10.1021/ol900306v. PMID: 19320508 (with free text available).
- Okauchi, T.; Itonaga, M.; Minami, T.; Owa, T.; Kitoh, K.; Yoshino, H. A General Method for Acylation of Indoles at the 3-Position with Acyl Chlorides in the Presence of Dialkylaluminum Chloride. Org. Lett. 2000, 2 (10), 1485–1487 DOI: 10.1021/ol005841p.
edited Apr 30 at 12:40
Martin - マーチン♦
34.1k9112240
answered Apr 29 at 11:57
WaylanderWaylander
7,36911726
$endgroup$
add a comment |
$begingroup$
The heterocycle in this question is indole and is aromatic. This means that the N lone pair is delocalised and not readily available for nucleophilic attack. Think of it as similar in reactivity to a secondary amide nitrogen RCONHR. Generally you need to formally deprotonate to functionalise, though there are some interesting techniques using carbonyl azoles catalysed by DBU[1] and others using aldehyde and alcohol substrates.[2] Note that 3-unsubstituted indoles react with acyl halides by F-C acylation at the 3 position.[3]
References:
- Heller, S. T.; Schultz, E. E.; Sarpong, R. Chemoselective N-Acylation of Indoles and Oxazolidinones with Carbonylazoles. Angew. Chem. Int. Ed. 2012, 51 (33), 8304–8308 DOI: 10.1002/anie.201203976.
- Maki, B. E.; Scheidt, K. A. Single-Flask Synthesis ofN-Acylated Indoles by Catalytic Dehydrogenative Coupling with Primary Alcohols. Org. Lett. 2009, 11 (7), 1651–1654 DOI: 10.1021/ol900306v. PMID: 19320508 (with free text available).
- Okauchi, T.; Itonaga, M.; Minami, T.; Owa, T.; Kitoh, K.; Yoshino, H. A General Method for Acylation of Indoles at the 3-Position with Acyl Chlorides in the Presence of Dialkylaluminum Chloride. Org. Lett. 2000, 2 (10), 1485–1487 DOI: 10.1021/ol005841p.
edited Apr 30 at 12:40
Martin - マーチン♦
34.1k9112240
answered Apr 29 at 11:57
WaylanderWaylander
7,36911726
$endgroup$
add a comment |
$begingroup$
The heterocycle in this question is indole and is aromatic. This means that the N lone pair is delocalised and not readily available for nucleophilic attack. Think of it as similar in reactivity to a secondary amide nitrogen RCONHR. Generally you need to formally deprotonate to functionalise, though there are some interesting techniques using carbonyl azoles catalysed by DBU[1] and others using aldehyde and alcohol substrates.[2] Note that 3-unsubstituted indoles react with acyl halides by F-C acylation at the 3 position.[3]
References:
- Heller, S. T.; Schultz, E. E.; Sarpong, R. Chemoselective N-Acylation of Indoles and Oxazolidinones with Carbonylazoles. Angew. Chem. Int. Ed. 2012, 51 (33), 8304–8308 DOI: 10.1002/anie.201203976.
- Maki, B. E.; Scheidt, K. A. Single-Flask Synthesis ofN-Acylated Indoles by Catalytic Dehydrogenative Coupling with Primary Alcohols. Org. Lett. 2009, 11 (7), 1651–1654 DOI: 10.1021/ol900306v. PMID: 19320508 (with free text available).
- Okauchi, T.; Itonaga, M.; Minami, T.; Owa, T.; Kitoh, K.; Yoshino, H. A General Method for Acylation of Indoles at the 3-Position with Acyl Chlorides in the Presence of Dialkylaluminum Chloride. Org. Lett. 2000, 2 (10), 1485–1487 DOI: 10.1021/ol005841p.
edited Apr 30 at 12:40
Martin - マーチン♦
34.1k9112240
answered Apr 29 at 11:57
WaylanderWaylander
7,36911726
$endgroup$
The heterocycle in this question is indole and is aromatic. This means that the N lone pair is delocalised and not readily available for nucleophilic attack. Think of it as similar in reactivity to a secondary amide nitrogen RCONHR. Generally you need to formally deprotonate to functionalise, though there are some interesting techniques using carbonyl azoles catalysed by DBU[1] and others using aldehyde and alcohol substrates.[2] Note that 3-unsubstituted indoles react with acyl halides by F-C acylation at the 3 position.[3]
References:
- Heller, S. T.; Schultz, E. E.; Sarpong, R. Chemoselective N-Acylation of Indoles and Oxazolidinones with Carbonylazoles. Angew. Chem. Int. Ed. 2012, 51 (33), 8304–8308 DOI: 10.1002/anie.201203976.
- Maki, B. E.; Scheidt, K. A. Single-Flask Synthesis ofN-Acylated Indoles by Catalytic Dehydrogenative Coupling with Primary Alcohols. Org. Lett. 2009, 11 (7), 1651–1654 DOI: 10.1021/ol900306v. PMID: 19320508 (with free text available).
- Okauchi, T.; Itonaga, M.; Minami, T.; Owa, T.; Kitoh, K.; Yoshino, H. A General Method for Acylation of Indoles at the 3-Position with Acyl Chlorides in the Presence of Dialkylaluminum Chloride. Org. Lett. 2000, 2 (10), 1485–1487 DOI: 10.1021/ol005841p.
edited Apr 30 at 12:40
Martin - マーチン♦
34.1k9112240
answered Apr 29 at 11:57
WaylanderWaylander
7,36911726
edited Apr 30 at 12:40
Martin - マーチン♦
34.1k9112240
edited Apr 30 at 12:40
Martin - マーチン♦
34.1k9112240
edited Apr 30 at 12:40
Martin - マーチン♦
34.1k9112240
34.1k9112240
answered Apr 29 at 11:57
WaylanderWaylander
7,36911726
answered Apr 29 at 11:57
WaylanderWaylander
7,36911726
answered Apr 29 at 11:57
WaylanderWaylander
7,36911726
7,36911726
add a comment |
add a comment |
$begingroup$
If you consider the lone pair on that N-atom and apply Hückel's (4n+2)π-e rule to check aromaticity , it satisfies all the conditions. So in order to achieve aromatic-stabilisation the nitrogen's valency is no more available for condensation!
answered Apr 29 at 13:41
ANBENZENEANBENZENE
1436
$endgroup$
$begingroup$
Hückel's rules should not be applied to this compound for two facts: 1. It is not a mono-cycle. 2. It is a heterocycle. It would be by far superior, at a more fundamental level, and even simpler to just state that the lone pair is delocalised. One could even show this with resonance structures, but that might be overkill.
$endgroup$
– Martin - マーチン♦
Apr 30 at 12:51
$begingroup$
Why can't we apply Hückel's rule? I didn't know that; would you please elaborate?
$endgroup$
– ANBENZENE
Apr 30 at 13:39
$begingroup$
Related: Is pyrene aromatic despite failing Hückel's rule? Do lone pairs on substituents (e.g. in aniline) count towards Hückel's rule? What is the justification for Hückel's rule? Applying Huckel's rule to non-planar compounds My answer covers it also: What is Y-aromaticity? Is the trinitromethanide anion aromatic?
$endgroup$
– Martin - マーチン♦
Apr 30 at 13:58
1
$begingroup$
Tl;dr: there are three criteria for which the rule has been observed. 1. monocyclic planar, 2. trigonal/diagonal hybridised atoms 3. (4n+2) pi electrons, n should not exceed 5. The calculations were done for $ce(CH)_m$, so they strictly only hold for these compounds. The third criteria has been used so often (and most of the times wrong) and is incredibly popular (also wrong), that it is perceived as Hückel's rule (also wrong). It is painful to see that it is taught like this, without teaching the underlying theory, which is possibly simpler than learning about the exceptions.
$endgroup$
– Martin - マーチン♦
Apr 30 at 14:05
add a comment |
$begingroup$
If you consider the lone pair on that N-atom and apply Hückel's (4n+2)π-e rule to check aromaticity , it satisfies all the conditions. So in order to achieve aromatic-stabilisation the nitrogen's valency is no more available for condensation!
answered Apr 29 at 13:41
ANBENZENEANBENZENE
1436
$endgroup$
$begingroup$
Hückel's rules should not be applied to this compound for two facts: 1. It is not a mono-cycle. 2. It is a heterocycle. It would be by far superior, at a more fundamental level, and even simpler to just state that the lone pair is delocalised. One could even show this with resonance structures, but that might be overkill.
$endgroup$
– Martin - マーチン♦
Apr 30 at 12:51
$begingroup$
Why can't we apply Hückel's rule? I didn't know that; would you please elaborate?
$endgroup$
– ANBENZENE
Apr 30 at 13:39
$begingroup$
Related: Is pyrene aromatic despite failing Hückel's rule? Do lone pairs on substituents (e.g. in aniline) count towards Hückel's rule? What is the justification for Hückel's rule? Applying Huckel's rule to non-planar compounds My answer covers it also: What is Y-aromaticity? Is the trinitromethanide anion aromatic?
$endgroup$
– Martin - マーチン♦
Apr 30 at 13:58
1
$begingroup$
Tl;dr: there are three criteria for which the rule has been observed. 1. monocyclic planar, 2. trigonal/diagonal hybridised atoms 3. (4n+2) pi electrons, n should not exceed 5. The calculations were done for $ce(CH)_m$, so they strictly only hold for these compounds. The third criteria has been used so often (and most of the times wrong) and is incredibly popular (also wrong), that it is perceived as Hückel's rule (also wrong). It is painful to see that it is taught like this, without teaching the underlying theory, which is possibly simpler than learning about the exceptions.
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– Martin - マーチン♦
Apr 30 at 14:05
add a comment |
$begingroup$
If you consider the lone pair on that N-atom and apply Hückel's (4n+2)π-e rule to check aromaticity , it satisfies all the conditions. So in order to achieve aromatic-stabilisation the nitrogen's valency is no more available for condensation!
answered Apr 29 at 13:41
ANBENZENEANBENZENE
1436
$endgroup$
If you consider the lone pair on that N-atom and apply Hückel's (4n+2)π-e rule to check aromaticity , it satisfies all the conditions. So in order to achieve aromatic-stabilisation the nitrogen's valency is no more available for condensation!
answered Apr 29 at 13:41
ANBENZENEANBENZENE
1436
answered Apr 29 at 13:41
ANBENZENEANBENZENE
1436
answered Apr 29 at 13:41
ANBENZENEANBENZENE
1436
answered Apr 29 at 13:41
ANBENZENEANBENZENE
1436
1436
$begingroup$
Hückel's rules should not be applied to this compound for two facts: 1. It is not a mono-cycle. 2. It is a heterocycle. It would be by far superior, at a more fundamental level, and even simpler to just state that the lone pair is delocalised. One could even show this with resonance structures, but that might be overkill.
$endgroup$
– Martin - マーチン♦
Apr 30 at 12:51
$begingroup$
Why can't we apply Hückel's rule? I didn't know that; would you please elaborate?
$endgroup$
– ANBENZENE
Apr 30 at 13:39
$begingroup$
Related: Is pyrene aromatic despite failing Hückel's rule? Do lone pairs on substituents (e.g. in aniline) count towards Hückel's rule? What is the justification for Hückel's rule? Applying Huckel's rule to non-planar compounds My answer covers it also: What is Y-aromaticity? Is the trinitromethanide anion aromatic?
$endgroup$
– Martin - マーチン♦
Apr 30 at 13:58
1
$begingroup$
Tl;dr: there are three criteria for which the rule has been observed. 1. monocyclic planar, 2. trigonal/diagonal hybridised atoms 3. (4n+2) pi electrons, n should not exceed 5. The calculations were done for $ce(CH)_m$, so they strictly only hold for these compounds. The third criteria has been used so often (and most of the times wrong) and is incredibly popular (also wrong), that it is perceived as Hückel's rule (also wrong). It is painful to see that it is taught like this, without teaching the underlying theory, which is possibly simpler than learning about the exceptions.
$endgroup$
– Martin - マーチン♦
Apr 30 at 14:05
add a comment |
$begingroup$
Hückel's rules should not be applied to this compound for two facts: 1. It is not a mono-cycle. 2. It is a heterocycle. It would be by far superior, at a more fundamental level, and even simpler to just state that the lone pair is delocalised. One could even show this with resonance structures, but that might be overkill.
$endgroup$
– Martin - マーチン♦
Apr 30 at 12:51
$begingroup$
Why can't we apply Hückel's rule? I didn't know that; would you please elaborate?
$endgroup$
– ANBENZENE
Apr 30 at 13:39
$begingroup$
Related: Is pyrene aromatic despite failing Hückel's rule? Do lone pairs on substituents (e.g. in aniline) count towards Hückel's rule? What is the justification for Hückel's rule? Applying Huckel's rule to non-planar compounds My answer covers it also: What is Y-aromaticity? Is the trinitromethanide anion aromatic?
$endgroup$
– Martin - マーチン♦
Apr 30 at 13:58
1
$begingroup$
Tl;dr: there are three criteria for which the rule has been observed. 1. monocyclic planar, 2. trigonal/diagonal hybridised atoms 3. (4n+2) pi electrons, n should not exceed 5. The calculations were done for $ce(CH)_m$, so they strictly only hold for these compounds. The third criteria has been used so often (and most of the times wrong) and is incredibly popular (also wrong), that it is perceived as Hückel's rule (also wrong). It is painful to see that it is taught like this, without teaching the underlying theory, which is possibly simpler than learning about the exceptions.
$endgroup$
– Martin - マーチン♦
Apr 30 at 14:05
$begingroup$
Hückel's rules should not be applied to this compound for two facts: 1. It is not a mono-cycle. 2. It is a heterocycle. It would be by far superior, at a more fundamental level, and even simpler to just state that the lone pair is delocalised. One could even show this with resonance structures, but that might be overkill.
$endgroup$
– Martin - マーチン♦
Apr 30 at 12:51
$begingroup$
Hückel's rules should not be applied to this compound for two facts: 1. It is not a mono-cycle. 2. It is a heterocycle. It would be by far superior, at a more fundamental level, and even simpler to just state that the lone pair is delocalised. One could even show this with resonance structures, but that might be overkill.
$endgroup$
– Martin - マーチン♦
Apr 30 at 12:51
$begingroup$
Why can't we apply Hückel's rule? I didn't know that; would you please elaborate?
$endgroup$
– ANBENZENE
Apr 30 at 13:39
$begingroup$
Why can't we apply Hückel's rule? I didn't know that; would you please elaborate?
$endgroup$
– ANBENZENE
Apr 30 at 13:39
$begingroup$
Related: Is pyrene aromatic despite failing Hückel's rule? Do lone pairs on substituents (e.g. in aniline) count towards Hückel's rule? What is the justification for Hückel's rule? Applying Huckel's rule to non-planar compounds My answer covers it also: What is Y-aromaticity? Is the trinitromethanide anion aromatic?
$endgroup$
– Martin - マーチン♦
Apr 30 at 13:58
$begingroup$
Related: Is pyrene aromatic despite failing Hückel's rule? Do lone pairs on substituents (e.g. in aniline) count towards Hückel's rule? What is the justification for Hückel's rule? Applying Huckel's rule to non-planar compounds My answer covers it also: What is Y-aromaticity? Is the trinitromethanide anion aromatic?
$endgroup$
– Martin - マーチン♦
Apr 30 at 13:58
1
1
$begingroup$
Tl;dr: there are three criteria for which the rule has been observed. 1. monocyclic planar, 2. trigonal/diagonal hybridised atoms 3. (4n+2) pi electrons, n should not exceed 5. The calculations were done for $ce(CH)_m$, so they strictly only hold for these compounds. The third criteria has been used so often (and most of the times wrong) and is incredibly popular (also wrong), that it is perceived as Hückel's rule (also wrong). It is painful to see that it is taught like this, without teaching the underlying theory, which is possibly simpler than learning about the exceptions.
$endgroup$
– Martin - マーチン♦
Apr 30 at 14:05
$begingroup$
Tl;dr: there are three criteria for which the rule has been observed. 1. monocyclic planar, 2. trigonal/diagonal hybridised atoms 3. (4n+2) pi electrons, n should not exceed 5. The calculations were done for $ce(CH)_m$, so they strictly only hold for these compounds. The third criteria has been used so often (and most of the times wrong) and is incredibly popular (also wrong), that it is perceived as Hückel's rule (also wrong). It is painful to see that it is taught like this, without teaching the underlying theory, which is possibly simpler than learning about the exceptions.
$endgroup$
– Martin - マーチン♦
Apr 30 at 14:05
add a comment |
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$begingroup$
Secondary amine group shown here is quite sterically hindered..Approach at Burgi-Dunitz trajectory would most probably be difficult
$endgroup$
– YUSUF HASAN
Apr 29 at 9:16
$begingroup$
Did you mean lone pair of electron in N is less available for carbocation to be attacked? @YUSUFHASAN
$endgroup$
– Amar30657
Apr 29 at 9:27
$begingroup$
No..I mean what you have in mind is a nucleophilic attack by NH on CH3COCl as the first step, right? So that would be retarded by steric hindrance..
$endgroup$
– YUSUF HASAN
Apr 29 at 9:29
4
$begingroup$
Nothing to do with sterics. The lone pair on the nitrogen is delocalised into the aromatic system so is not available for nucleophilic attack. If you want to functionalise the indole-NH you generally have to formally deprotonate with strong base. Otherwise it reacts as an enamine through the 3-position.
$endgroup$
– Waylander
Apr 29 at 9:53
1
$begingroup$
@Amar30657 You need to read more about aromatic systems. en.wikipedia.org/wiki/Indole
$endgroup$
– Waylander
Apr 29 at 10:05