Sciencemadness Discussion Board

Indole identification questions (para-Dimethylaminobenzaldehyde)

PhenethylamineMachine - 8-5-2018 at 07:02

Strips of filter paper are saturated with para-Dimethylaminobenzaldehyde in 45% EtOH, and are air dried. A small amount of the indole substance is placed into a few drops of EtOH, then, one of the dried para-Dimethylaminobenzaldehyde saturated strips of filter paper is soaked in this and allowed to dry. Next, one drop of concentrated HCL is placed on the dried paper.

Here is my question: technically could the powdered indole substance be placed directly on the dried strip of para-Dimethylaminobenzaldehyde saturated filter paper where a drop of HCL can then be placed directly on it?

Miscellaneous comment:

one of my colleagues was performing experiments with 1-acetyl-lysergic acid diethylamide and 1-propionyl-lysergic acid diethylamide and indole identification reagents such as para-Dimethylaminobenzaldehyde

My colleague's findings were that 1-acetyl-lysergic acid diethylamide and 1-propionyl-lysergic acid diethylamide were not producing any type of color change reaction when combined with these indole identification reagents.
(A note was made that possibly a slight yellow color was being produced, however, I feel this was nothing, maybe something to do with the paper these compounds were on, but nothing to be paid any attention to.)

My opinion was that such an experiment was doomed from the start simply because the acetyl or propionyl substitutions are attached to the NH hydrogen of the pyrrole ring moiety on both compounds, therefore these compounds are not indoles, (... as they do not contain an indole ring moiety as part of their structure, they can not be considered indoles) So it should not have been any surprise that 1-acetyl-lysergic acid diethylamide and 1-propionyl-lysergic acid diethylamide did not respond to these indole identification reagents. ...though even after much debate my colleagues proceeded with the experiments.

Any comments?

One last quick question:

Oh, also, for the synthesis of p-nitrosodimethylaniline, the brief description below should be an efficient manner in which to proceed, no?

dimethylaniline is dissolved in dilute HCL and the solution is chilled to 0°c. Then a solution of sodium nitrate in H20 which has already been chilled to 0°c is added through a funnel. Vigorous stirring should be employed while the sodium nitrate solution is being added, and the flask should be maintained at freezing temperature with a NaCL/H20 freezing mixture. This addition must be made at such a rate as to prevent the temperature from ever rising over 5°c, (this should take around 40 minutes). At this point the precipitated crystals of p-nitrosodimethylaniline hydrochloride are vacuum filtered, and washed.

Comments? Are there any major errors? Are there better ways to proceed?




Sigmatropic - 8-5-2018 at 09:08

For that filter paper, I don't see why not and you should have all materials. Maybe you won't get even staining because the indole doesn't dissolve uniformly. Just give it a try and see.

substitution of a hetereoaromatic nucleus does not change it. It just alters its reactivity. A 1 substituted indole just reacts differently from its unsubstituted counterpart but is still very much an indole.

Apart from the mistake of writing nitrate instead of nitrite I don't see any major errors.

zed - 8-5-2018 at 14:06

I vaguely remember using wooden test strips and HCl to test for Indoles.

Though, that would have been quite a while ago.

Yep! Paragraph 5..... https://books.google.com/books?id=HXJKAAAAMAAJ&pg=PA301&...

Isn't this fun?

I'm thinking acetylation at the 1-position, inhibits(or stabilizes) the Indole ring from opening and/or polymerizing. Therefore, no beautiful color reaction.

https://en.wikipedia.org/wiki/Indigo_dye

Ahhh. Document containing structure of the ergot pigment in question.

https://www.unodc.org/pdf/scientific/SCITEC6.pdf

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PhenethylamineMachine - 11-5-2018 at 05:24

Quote: Originally posted by Sigmatropic  
For that filter paper, I don't see why not and you should have all materials. Maybe you won't get even staining because the indole doesn't dissolve uniformly. Just give it a try and see.

substitution of a hetereoaromatic nucleus does not change it. It just alters its reactivity. A 1 substituted indole just reacts differently from its unsubstituted counterpart but is still very much an indole.

Apart from the mistake of writing nitrate instead of nitrite I don't see any major errors.


Yup, tried it out, it works perfectly, maybe slightly less uniform, but overall no issues.

Moving on to the next subject:

Yeah, that was a huge part of the debate, the argument on their part was very similar to yours, that substitution of a hetereoaromatic nucleus does not produce a new compound, but alters the reactivity of the one present. I am still having slight issues with being able to fully grock the concept as it has not been properly explained to me.


As for the typographical error, mea culpa, as I explained before I am for the most part an autodidact in this field.

I have access to a laboratory as well as access to the knowledge of the retired chemist who owns it, but I only visit the lab one or two times in a month, the majority of the time I am reading books or working in the notebook on my own, so I don't have any help or guidance while learning most of this stuff.

In all honesty I think in an doing pretty well for an autodidact, but yeah, I do make silly mistakes from time to time.

PhenethylamineMachine - 11-5-2018 at 05:29

Quote: Originally posted by zed  
I vaguely remember using wooden test strips and HCl to test for Indoles.

Though, that would have been quite a while ago.

Yep! Paragraph 5..... https://books.google.com/books?id=HXJKAAAAMAAJ&pg=PA301&...

Isn't this fun?

I'm thinking acetylation at the 1-position, inhibits(or stabilizes) the Indole ring from opening and/or polymerizing. Therefore, no beautiful color reaction.

https://en.wikipedia.org/wiki/Indigo_dye

Ahhh. Document containing structure of the ergot pigment in question.

https://www.unodc.org/pdf/scientific/SCITEC6.pdf

[Edited on 8-5-2018 by zed]

[Edited on 8-5-2018 by zed]

[Edited on 8-5-2018 by zed]

[Edited on 8-5-2018 by zed]

[Edited on 9-5-2018 by zed]

[Edited on 9-5-2018 by zed]

[Edited on 9-5-2018 by zed]


Hmm...

Interesting thoughts regarding the failure of the N1 substituted lysergamides to produce a color change reaction... Regardless, it all comes down to those substitutions on nitrogen 1, I just had the explanation and reasoning incorrectly interpreted.

...I am researching now to obtain a full and correct understanding of the mechanisms at play.

...All of this discussion helps

PhenethylamineMachine - 14-5-2018 at 05:56

So, no other comments regarding N1 substituted lysergamides and their failure to react with indole identification reagents?

This subject was of particular interest to me.

I signed up for laboratory use next week, and if I have the time I will look further into this matter. I might have some free time, as I am supposed to start a reaction which involves placing tryptamine base in IPA which is then treated with propyliodide and diisopropylethylamine and allowed to stir at room temperature for 36 hours, so while I am allowing my reaction mixture to stir for 36 hours I will have time to work on small side projects, such as the N1 substituted lysergamides and indole identification reagents.

zed - 14-5-2018 at 18:32

Try the woodstrip HCl test. Nice color!

Though I think it will not work for your 1 Acetyl type Indoles.

PhenethylamineMachine - 16-5-2018 at 05:10

Quote: Originally posted by zed  
Try the woodstrip HCl test. Nice color!

Though I think it will not work for your 1 Acetyl type Indoles.


The filter paper strips work great. Actually the method I described in my initial post has been more than satisfactory.

Though just out of curiosity, why are you so keen on these wood strips?

Responding to the next topic in your post:

Yeah, that was the issue, why are the N1 substituted lysergamides not reacting with indole identification reagents? My guess was that because the substitutions were being made to the NH of the pyrrole ring moiety that the compounds were no longer considered indoles, however, others have suggested that the compounds are in fact still indoles, but that their reactivity has been altered as a result.

I was just seeking some clarity, or a good explanation of what is going on here.

I signed up for lab time next week, and I would like to have this sorted out before my scheduled laboratory visit. (I actually have tons of higher priority projects, but as I explained I might have 36 hours while a reaction is stirring to work on other smaller and less important projects. )

zed - 25-5-2018 at 12:48

Still indoles, of course! Just not reactive to standard test reagents anymore!

Woodstrips? Low-tech production.....Cheap, easily acquired. Crimson color reaction.

Fun?

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