04-16-03 18:46
No 427301
curious if bees might be able to suggest alternatives to Aliquat 336 as a PTC. Antibody is specifically curious about the viability of polysorbate as a replacement in Barium's new C=C reduction variation.
opinions? alternatives?
(Hive Bee)
04-16-03 22:11
No 427352
Hxadecyltrimethylammonium bromide ("Cetrimide") is still quite lipophilic so maybe it can substitute for Aliquat 336. It is cheap and easy to get, as it is used in the preparation of shampoo's :
http://www.hkmj.org.hk/skin/govformu.htm
Don't know if a polysorbate will work, do you have any refs on the subject ?
What about PEG400?
http://www.ealasaid.com/fan/lorrelibrary
(Hive Addict)
04-17-03 00:06
No 427384
interesting link, vitus. no i've no refs just a litre of polysorbate 20
just did a couple of tests and while the polysorbate 20 seems to disolve in either toluene or dcm, when water is added regardless of the amount of stirring the aqueous layer reforms above the dcm. With toluene addition of water causes this puss like suspension (it stays suspended). Never having worked with PTC's before its difficult to say whether it was truly successful or not.
its looks as though it may complicate work-up
(Moderator)
04-17-03 00:37
No 427398
Why should polysorbate act as a PTC for organic compounds?
(Chief Bee)
04-17-03 01:34
No 427415
Polyethyleneglycols with molecular weights of 200-600 (particularly PEG 400) works very good as a PTC, and can usually be crashed out from the organic phase by dilution with ether...
In some reactions the free OH groups can also be modified to bear other substituents to modify its properties, for example by attaching phenylphosphines and adding Pd salts you can make a recoverable homogenous catalyst support for all kinds of Pd-catalyzed reactions, as a substitute for Pd(PPh3)3. Example: Post 446706 (Rhodium: "PEG as support/PTC in Pd-catalyzed cross-couplings", Chemistry Discourse)
(Hive Bee)
04-17-03 02:34
No 427429
Check out Post 290770 (foxy2: "Right one", Chemicals & Equipment). Yes, it is quite ghetto but at least they tested several fabric softeners. Comfort worked quite well.
(Distinctive Doe)
04-17-03 04:41
No 427465
moo
Since you seem to have the article, maybe you could post the details?
Or is this basically all there is?
Comfort worked quite well.
(Hive Bee)
04-17-03 09:57
No 427515
(Rated as: excellent)
Most of the article discusses educational aspects of the reaction so I'll type the parts that most benefit bees along with the test reaction so that it is clear how they tested it. It is basically the addition of dichlorocarbene, generated from NaOH and CHCl3 under PTC conditions, to cyclohexene. This is the article that makes me grin whenever walking past the fabric softeners in the supermarket.
Fabric Softeners as Phase Transfer Catalysts in Organic Synthesis, J. Chem. Educ. 68, 69-70 (1991):
[...]
Experimental
[...]
To 10 mL of 50% (w/w) aqueous sodium hydroxide solution in a 100-mL round-bottom flask was added 5 mL of cyclohexene and 20 mL of chloroform. Then 2 mL of the fabric softener to be tested was added to the mixture. The stoppered two-phase mixture was stirred magnetically at ~1000 rpm using a 1-in. Teflon-coated stirring bar. The reaction mixture turned turbid as some white emulsion started to form after 15 to 20 min.
The reaction was monitored by GC at 15- to 20-min time intervals. The stirrer was turned off, and 1-mL GC samples were taken from the top organic layer of reaction mixture. The samples were passed through some anhydrous sodium sulfate packed in a Pasteur pipet to remove any of the white emulsion and moisture. The GC experiments were carried out using a 3 mm X 1 m SE-30 column installed in a Hitachi 163 gas chromatograph with flame ionization detector and a Hitachi 561 recorder. In a larger scale experiment, 15 mL of the sodium hydroxide solution, 20 mL of chloroform, 20 mL of cyclohexene, and 8 mL of the fabric softener were stirred for 5 h as above. after simple work up and distillation (collected between 192-198 °C), NMR pure 7,7-dichlorobicyclo[4.1.0]heptane was obtained in 51% Yield1.
Results and Discussion
The reaction times of each fabric softener used were summarized in the table. For 2 mL of the fabric softeners used, the reactions were completed within 2 h with the exception of one brand (run 4, table). Two control experiments were also carried out. Without the fabric softener, the reaction did not proceed as indicated by GC. When a typical phase transfer catalyst, Aliquat 336 (methyltrioctylammonium chloride, 2 mol % to cyclohexene) was used in the reaction, the reaction was also completed in 2 h. This indicated that the effect of 2 mL of fabric softener was roughly equivalent to that of 2 mol % of a typical phase transfer catalyst.
One sample tried did not work well as a phase transfer catalyst (run 4, table). It may be due to the fact that another active ingredient such as noncationic softening agent was used in the formula. It is also worth noting that the concentrated formula (run 3) did not work better as a phase transfer agent than the regular formula (run 2).
Place of Reaction
Fabric softener Manufacture cents/mL time (h)
------------------------------------------------ --------
1. Soft Great Japan 0.14 1.50
2. Comfort UK 0.16 1.33
3. Concentrated Comfort UK 0.23 1.33
4. Bonnie Hubbard Canada 0.12 >4a
5. Softlan US 0.13 2.00
6. Park'n Hong Kong 0.11 1.00
------------------------------------------------ --------
aReaction was not completed after 4 h.
[...]
References
1. J. Chem. Educ. 55, 350 and 429 (1978)
(Hive Addict)
04-18-03 18:31
No 427854
they use it straight out of the bottle, wow. thanx moo
(Stranger)
04-20-03 19:03
No 428209
I am also v.interested in this, particularly as to the possibility of whether BzEt3N would bee a suitable substitute for Aliquat 336 in Barium's 2-phase borohydride redn.? Can anyone offer any light on this?
Thanks!
(Hive Bee)
04-20-03 21:39
No 428228
Aliquat 336, or methyltrioctylammonium chloride, is a very lipophilic PTC (more than 20 C atoms), BzEt3N+ Cl- is quite hydrophilic.
On the other hand, "Phase Transfer Catalysts, properties and applications" (Merck-Schuchardt) states that tetraalkylammonium borohydrides are soluble in organic solvents. So it might work.
http://www.ealasaid.com/fan/lorrelibrary
(Hive Bee)
04-21-03 01:21
No 428263
I've recently taken interest in the PTC chemistry. Not being very familiar with it and only guided by the readings available in March's 5th edition text i've taken the task to find a PTC catalyst that will remove a OH and convert to an alkane as well as reducing a carboxylic acid to an alcohol or alkane or aldehyde.
I have read of the OTC PTC, some being Fabric softeners and just the whole idea of doing chemistry in this way increases my interest.
So I guess the only dumb question is the one that doesn't get asked .................java
We're all in this world together,
http://www.chiapaslink.ukgateway.net/