Sciencemadness Discussion Board

pseudoisomethylionone by Aldol condensation of citral with methylethylketone

Fery - 29-11-2023 at 10:54

This experiment is a variation to this one, just a ketone with one more carbon was used and something had to be adjusted on the fly according surprises experienced:

pseudoionone by Aldol condensation of citral with acetone
https://www.sciencemadness.org/whisper/viewthread.php?tid=16...

experiment
In 1 L RBF was thoroughly mixed 205 g of rapidly magnetically stirred methylethylketone (99,7 % purity) of room temperature (it should not be ice cold, read later) with 6,33 g 40% NaOH (2,53 g NaOH + 3,8 g water). It did not fully mix with MEK unlike with acetone, solubility of water in MEK is only 10% at 20 C and much less when conc. water solution of NaOH. Then immediately 102,0 g of previously vacuum distilled citral (0,67 mol) was added while continued rapid magnetic stirring. Heating commenced and set to 40 C on heating mantle (perhaps it would be better to set to 60 C since the beginning, read later the reason, MEK does not boil at 60 C unlike acetone), the reaction was only slightly exothermic (much less than with acetone very likely due poor miscibility of conc. water solution of NaOH with MEK). When T reached 40 C, the time was started to count and continued rapid magnetic stirring (the faster the better due to poor miscibility). Mouths of flask covered with plastic sheets fixed with rubber bands to prevent air oxidation of citral. The temperature spontaneously reached peak 45 C but later fell to 40 C at which it was kept for the rest of time by the heating mantle (it would be very likely better to keep it at 60 C, read later). Meanwhile I studied more materials online and found that MEK is bound into methylene group if using HCl gas (luckily I used NaOH) and in one experiment when NaOH catalytically condensing MEK with an aldehyde obtained from alfa pinene they used even temperatures -10 to 0 C to make bond to -CH2- group. While methyl group -CH3 is bound at higher temperatures if using NaOH (in one experiement they used 60-65 C). So after 1,5 h at 40 C I decided to increase the temperature to 60 C at which the reaction was kept for another 90 minutes. This reaction is slower than with acetone due to poor miscibility of catalyst and also higher temperature favors binding methyl group.

d3ra00906h-f11.jpg - 29kB

After 90 minutes of rapid stirring at 60 C the reaction was stopped by addition of 9 g citric acid monohydrate in small amount of water while magnetically stirring (prior neutralization if stirring stopped the catalyst water solution of NaOH quickly settled at the bottom).

2-butanone distilled out at and very likely the water due to less difference in their boiling points than when using acetone. When the ketone was distilled out and still small amount of water present the distillation clearly change its typical sound into something like when you fry schnitzels on hot pan with fat/oil. Na mono/dihydrogencitrate salts appeared flying in the flask like a donut (that's why it was essential to stir during the distillation to prevent bumping and local overheating !!!)

193,6 g turbid distillate collected in receiving flask (MEK+water). After settling a little of water separated as bottom layer (almost invisible, only very small amount like 2-5 ml) and both layers become clear, water was salted out using CaCl2 to recover MEK, solubility of water in MEK 10% at 20 C.

Red crude product from distillation flask was washed 4x100 ml water in 250 ml sep. funnel, obtained 124,7 g = 0,60 mol (M=206,33 g/mol) of wet product. Dried with anh. CaCl2, 122 g = 0,59 mol of the product.

Predistilled at water aspirator level vacuum using lazy setup without condenser (just cooling directly attached receiving flask with a snow, there is a winter here now), T in distil flask approx 130 C, collected 40,3 g distillate (but you can collect less and separate forerun later at stronger vacuum level). Here most of the unreacted citral present and also few drops of water although previously drying with CaCl2. It is very good to remove all the moist / water before stronger vacuum distillation, also degassing the content to be distilled at first with weaker vacuum.

Vacuum distilled using the same 2-stage oil rotary vane vacuum pump used for citral distillation.
Collected forerun upto 112 C, cca 5 ml.
Collected main fraction b.p. 112-125 C, 52 ml.



here materials why here the temperature is better 60 C than using lower T:

https://www.journal.csj.jp/doi/10.1246/bcsj.27.131
In the condensation of benzaldehyde with methyl ethyl ketone by aqueous sodium hydroxide, the lowered reaction temperature (3∼5°) favored the aldol condensation at the α-methylene group of the ketone as in the condensation of furfural with the ketone. On the other hand, the elevated reaction temperature (60∼65°) conducted exclusively the condensation at the α-methyl group of the ketone, giving 1-phenyl-1-penten-3-one (I). 3-Methyl-4-phenyl-4-butanol-2-one (II), obtained by the aldol condensation at the lowered reaction temperature (3∼5°)

https://www.thevespiary.org/library/Files_Uploaded_by_Users/...
when aqueous NaOH was employed as the condensing agent, benzaldehyde condensed with methyl ethyl ketone at the alfa methyl group of the ketone at ordinary temperature, forming 1-phenyl-1-penten-3-one, and, when hydrogen chloride was employed as the condensating agent, benzaldehyde reacted with methyl ethyl ketone at its alfe methylene group, giving 3-methyl-4-phenyl-3-buten-2-one.
...
furfural condensed with MEK by aqeous NaOH at its methylene group at the lowered reaction temperature 0-5 C,... condensed at its alfa methyl group at 60-65 C



photos



beginning of the reaction, it looks smooth but the catalyst is poorly miscible

IMG_20231128_084445_4.jpg - 65kB



nonetheless the reaction proceeds, here after 15 minutes just before reaching 40 C

IMG_20231128_085928_7.jpg - 74kB



after 90 minutes at 40 C (note it would be very likely better to heat it to 60 C)

IMG_20231128_104116_9.jpg - 66kB



after 90 minutes at 60 C, almost the same color

IMG_20231128_122811_2.jpg - 56kB



after neutralization with excess concentrated water solution of citric acid

IMG_20231128_122917_2.jpg - 48kB



distilling out MEK under necessary magnetic stirring, at the end a cake of Na mono/dihydrogencitrates flying at the surface like a donut

IMG_20231128_125700_1.jpg - 113kB IMG_20231128_140203_4.jpg - 38kB



transferred into sep. funnel to be washed with H2O

IMG_20231128_153732_3.jpg - 76kB


washing 4x with 100 ml water and then dried with CaCl2

IMG_20231128_165534_5.jpg - 67kB

[Edited on 29-11-2023 by Fery]

Fery - 29-11-2023 at 11:19

dry crude product going to be predistilled at water aspirator pump vacuum level

IMG_20231129_073733_5.jpg - 74kB



lazy setup for vacuum predistillation at water aspirator pump vacuum level (degassing, removing last traces of MEK and moist), receiving flask directly connected without messing condenser, receiving flask cooled by a snow

IMG_20231129_080259_3.jpg - 57kB IMG_20231129_082902_3.jpg - 72kB



product in the distillation flask after removing lower boiling point contaminants

IMG_20231129_091152_2.jpg - 75kB



distillate collected, a lot of unreacted citral and few drops of water (weight 40 g)

IMG_20231129_091208_2.jpg - 55kB IMG_20231129_091253_9.jpg - 64kB



full vacuum distillation using regular setup (also a condenser present)

IMG_20231129_151331_1.jpg - 100kB



collecting forerun, cca 5 ml (most of the unreacted citral already removed at predistillation at water aspirator pump vacuum level)

IMG_20231129_152239_5.jpg - 58kB IMG_20231129_152319_8.jpg - 57kB IMG_20231129_152332_5.jpg - 40kB



collecting main fraction 112-125 C

IMG_20231129_152435_5.jpg - 54kB IMG_20231129_152435_5.jpg - 54kB IMG_20231129_152509_1.jpg - 66kB IMG_20231129_152649_5.jpg - 59kB IMG_20231129_152728_3.jpg - 74kB IMG_20231129_152856_2.jpg - 74kB IMG_20231129_152910_9.jpg - 59kB IMG_20231129_153125_3.jpg - 65kB IMG_20231129_153133_3.jpg - 54kB IMG_20231129_153327_9.jpg - 75kB IMG_20231129_153336_5.jpg - 56kB



the product is pale yellow (very likely due to conjugated carbonyl C=O group with two C=C double bond groups)

IMG_20231129_181230_5.jpg - 61kB

Texium - 29-11-2023 at 18:30

Nice! Do you have any plans to further assess the purity of your product?

Fery - 29-11-2023 at 20:47

No way how to assess the purity.

I would like to perform a cyclization in 85% H3PO3 into alfa and in conc. H2SO4 into beta isomethylionone. Just to scent them. Description of their scents is very variable by different persons (genetic variability, hundreds of genes involved and hundreds of receptors).

https://www.scentree.co/en/Isoraldeine_95%C2%AE.html
Quote:
used for reproductions of violet notes, in floral fragrances, in association with rosy or woody sandalwood notes


http://www.thegoodscentscompany.com/data/rw1594721.html
alpha-isomethyl ionone
Quote:
orris woody floral fruit dried fruit violet jammy powdery tea


http://www.thegoodscentscompany.com/data/rw1045331.html
beta-isomethyl ionone
Quote:
woody ambergris waxy orris floral


https://colognoisseur.com/olfactory-chemistry-ionones-irones...
Quote:
Alpha-Methyl Ionone is softer and imparts the powdery quality to iris


https://basenotes.com/community/threads/difference-between-i...
Quote:
AJ Dave
Alpha isomethyl ionone smells like alpha ionone, but with the same "woody" smell now being the main smell. It also has a little bit of the the grape juice and prune juice smell, and also something creamy, almost like whipped cream. It's not my favorite.

Stefan.E
I also have alpha isomethyl ionone, isoraldeine 95 (my favorite). I have similar thoughts as AJ Dave, and Isoraldeine 95 is quite floral to me with the same ionone violet facet as the alpha.

Fery - 13-12-2023 at 11:11

This is very likely not pseudoisomethylionone but just pseudomethylionone. Comparing with the pseudoionone (citral + acetone), the extra methyl group of the pseudomethylionone (citral + butanone) seems to be on the "tail" of the molecule, so the "tail" is not branched. Like the molecule on the picture.
Pseudoisomethylionone = isoraldeine compared with pseudoionone has the same length of the "tail" and the extra CH3 group is attached to the third C of the "tail" part of the molecule so the "tail" is branched instead of linear. Moreover in the above isoraldeine link page they claim the scent of the alpha isomethylionone as:
Quote:
Floral, Orris, Woody, Powdery

But I do not scent anything woody after cyclization of the compound I obtained as described in the initial post of this thread. Which is even worse, I do now have any imagination what does mean "powdery" scent. I'm not any expert in scents, I just like them.
The cyclization product using 85% H3PO4 has very similar scent to alpha ionone so I'm just guessing I got a product which has the linear "tail" molecule that's without "iso". The branched variant (that's wiht the "iso") should have woody and powdery scent which I do not recognize.

Comparing these 3 compounds:

alpha ionone
Quote:
Boiling Point: 237 to 238 °C @ 760 mm Hg


alpha isomethylionone
Quote:
Boiling Point: 232 °C @ 760 Hg


alpha methylionone
Quote:
Boiling Point: 285 to 286 °C @ 760 mm Hg


The third one which I very likely got after cyclization in 85% H3PO4 (with linear "tail") should have much higher boiling point due to 1 carbon longer "tail". A similar effect could be observed in b.p. differences between linear n-hexane (b.p. 69 C) and branched isohexanes (b.p. 60-65 C). Here in isomethylionone / methylionone the difference >50 C seems to be like an error as the difference is just 1 carbon which changed position in 14 carbon molecule which is much smaller change than 1 positionally changed carbon in C6 (iso)hexanes.

Unfortunately I have only 5 ml of both alpha ionone and alpha methylionone which is unsuitable for distillation to measure preciously boiling points. I do not have such suitable small scale distillation apparatus and filling my smallest 50 ml flask with 5 ml sample is not good idea for precise measuring b.p. due to overheating walls of almost empty flask. Also the purity of alpha is never so good as purity of thermodymically most stable beta (it could be like 60% alpha + 20% beta + 20% gamma although according the color obtained it seems not to contain too much beta).



alpha ionone (citral + acetone -> pseudoionone -> cyclisation of pseudoionone in 85% H3PO4)

IMG_20231211_143331_5.jpg - 91kB



beta ionone (citral + acetone -> pseudoionone -> cyclisation of pseudoionone in 70 wt.% H2SO4 + 30 wt.% acetic acid) much more yellow / orange due to 2 conjugated C=C double bonds with carbonyl C=O group, it is easy to distinguish beta just due to its color, beta is always the most thermodynamically stable due to this conjugation, alpha as well gamma could be rearranged easily into beta by an action of conc. H2SO4

IMG_20231212_153901_1.jpg - 61kB



very likely alpha methylionone (citral + butanone (cat. NaOH, elevated temperature) -> very likely pseudomethylionone -> cyclisation of pseudomethylionone in 85% H3PO4) so this is a cyclization product from the compound dedicated to this thread

IMG_20231213_190258_0.jpg - 48kB



I wonder whether the branched variant, that's "pseudoisomethylionone is obtained at very low temperatures around 0 C using hydroxide catalyst. Because here they claim that it requires hydroxide + high temperatures
https://www.chemicalbook.com/ChemicalProductProperty_EN_CB51...

Quote:
Preparation:
By condensation of citral with methyl ethyl ketone controlling the ratio between the n- and iso-forms; the methyl pseudoionone obtained is then subjected to ring closure, using strong alkali and high temperature (thus favoring the formation of iso-forms)

But the alkali is used in the first step (citral + butanone) while cyclization (the second step) occurs in strong acids. They very likely posted some errors.

FM3 - 14-12-2023 at 10:14

I love seeing scent chemistry stuff, it is way overlooked given the fact it is the origin of all organic chemistry as we know it. Thanks!

Fery - 14-12-2023 at 21:48

These scents are really beautiful and natural. They are produced in plants and flowers by degradation of carotenoids. Glassware and everything has this nice scent during preparation and working with them is really pleasure. Everyone in EU can buy cheap citral from es-drei.de and there are certainly more suppliers in the world. Or at worst obtain citral from essential oil of lemongrass and others. The workup of the first step (aldol condensation of citral with ketone) requires vacuum distillation or there are also methods using bisulfite adduct or removing unreacted citral could be also done by steam distillation. I think even if the unreacted citral is not thoroughly removed then during the second step which is cyclization in conc. H3PO4 or H2SO4 it readily condenses into resinous sideproducts which stay in distillation flask while ionone passes into condensate during hydrodistillation.

Bedlasky - 2-1-2024 at 07:45

Quote: Originally posted by Fery  
No way how to assess the purity.


If you want, you can send me small samples and I can measure refractive indexes.