05-03-02 18:56
No 304605
SWIM has a question. The following was taken from Chromic's writeup on Rhodium's site. This is following the H2SO4 rearrangement.
<hr>
Let it cool. Load it into a sep funnel and pour off as much of the more dense ketone as possible (both PMP2P and MDP2P are more dense than water). Now extract with 3x20ml DCM.
<hr>
SWIM is confused. "pour off as much of the more dense ketone". Now extract with DCM. Extract what? Extract what is left in the sep funnel or what you just poured off into a beaker that has been reloaded into the sep funnel. SWIM is over analyzing this and need someone to reword this step.
Pardon my friend officer, He's a little slow.
(Hive Bee)
05-03-02 19:24
No 304611
Hi,
What he means is that you will have a 2 phase liquid in your flask. the top is the aqueous layer, the bottom is dirty ketone. The ketone is more dense, that's why. You'll tap it off(drain it) until you only have the top aqueous layer in your funnel. Then you extract that layer with the DCM(pour in an aliquot[20ml] of dcm, shake, wait for separation, drain off bottom small layer of dcm/ketone, repeat 3 times).
Hope this helps. Remember that organic chemistry is a loose art when it comes to wording. Know your densities to know which layer is on the top or bottom in extractions. KNow what happens to your extracted product when you add base or acid. In short, pay attention, and learn your chemistry if you wish for sucess.
Good luck
(Hive Bee)
05-03-02 19:33
No 304613
So let SWIM make sure this is correct. Tap/drain off the densed MD2P2 into a beaker. Left with water layer in sep funnel. Now use DCM to extract the last little bit of MD2P2 from the water layer and combine with the original part you drained from the bottom in the first step.
Pardon my friend officer, He's a little slow.
(Chief Bee)
05-03-02 22:48
No 304653
Superstar: exactly.
(Hive Addict)
05-04-02 01:16
No 304698
Rhodium, I think that particular sentence has confused 3 different people reading that write up. Would you care to replace the phase "pour off" with the phrase "drain off"? Thanks, and sorry about the confusion! I thought I made an alright technical writer... guess not!
(Greenhorn)
05-04-02 06:33
No 304777
Swim must admit, he actually got a little confused on this part himself. But once you do the synth and see everything you understand it. Trying to picture it in your head seems to mess swim up all the time.
We'll soon find out if I'm a chemist or not!
(I'm not Cheesie)
05-04-02 06:42
No 304779
Just how much MDP-2-P is able to be mixed in with the aqueous layer after tapping most of it off? Cheese always wondered about this, as MDP-2-P is NOT miscible with water so why even do the dcm extractions?
<Cheeseboy-a whiteboy with soul, like a black guy without soul
May De Sorce Bee Wit Chu-Always
(Hive Addict)
05-04-02 10:21
No 304821
Chromic has wondered too, but does the DCM extractions anyways... they're necessary for the washing at the end, for sure...
(Hive Bee)
05-04-02 22:03
No 304945
Chromic,
What do you mean the DCM extracts are necessary for the washing at the end? SWIM understand 2 times for DCM. Once for after the Oxone run. Once after the H2SO4 treatment. Someone, cheese or pickler, where suggesting that skipping both of these would be possible, just reduce yeilds? Do you agree?
Pardon my friend officer, He's a little slow.
(Hive Bee)
05-04-02 22:06
No 304946
Update Chromic,
SWIM needed to reread. Can't do the NaOH washes after the rearrangement without the DCM. Okay so no skip on that one but how bad do you think yields would hurt if skipping the first DCM extract? Seems like would save SWIM significant time since entire dist setup must be setup, cleaned, and stored each time (about 2hr process).
Pardon my friend officer, He's a little slow.
(Hive Addict)
05-04-02 23:07
No 304961
I've cut back on the amount of DCM a # of times in working up the rxn (no difference in yields), but I've never cut it out... sorry, no info.
(Chief Bee)
05-04-02 23:10
No 304962
Chromic: I have mofified your writeup according to your suggestion.
Superstar: After the ketone is tapped off, it cannot be properly washed with NaOH solution without being diluted with the combined DCM washes. Also, I believe you will lose at least 5% of your ketone if you are not extracting the aqueous layer as it easily forms an emulsion/suspension in the water. The NaOH washes are VERY good for purification of the ketone, as it removes any phenolic impurities/decomposition products and prevents those impurities to affect your product further down the road...
(Greenhorn)
05-04-02 23:12
No 304963
Swim skips the dcm extracts from both. If you filter the oxone before adding the iso to the mix, when it's done mixing, all the epoxide is at the bottom. There might be a tiny amount left, but time is money for swim. So Swim would rather lose a little $$$ and be able to do more runs. Just a personal choice. Why couldn't you skip the last dcm extract. Washings cause no problems for swim.
We'll soon find out if I'm a chemist or not!
(Hive Addict)
05-05-02 00:39
No 304989
Why not do multiple batches of epoxide, then process the epoxide to ketone all at once so you only do that step once?
(Greenhorn)
05-05-02 05:55
No 305078
That's exactly with swim does Chromic. Swim does 4 to 5 64gram batches and then does the h2so4 reflux. Much easier.
We'll soon find out if I'm a chemist or not!
(Hive Bee)
05-06-02 07:21
No 305315
I thought that the epoxide wasn't supposed to sit for long or it would rearrange to the glycol shich is not convertable or some shit. Or maybe I'm confusing it with the mdp2pol mehtod where to p2pol rearranges to the 1p and is useless. Input anybody?
(Greenhorn)
05-06-02 15:30
No 305399
The epoxide can sit, for how long, swim doesn't know. When you do the h2so4 rearrangment, the epoxide get rearranged to ketone and the glycol gets dehydrated to epoxide then to ketone. Both get rearranged to ketone. Weather you have epoxide or the glycol has to do with the ph of the oxone/meoh ph. If it's near 7, then you get epoxide. If it's more acidic, the you get the glycol. Both will yield ketone with the h2so4 rearrangement. If your doing the thermal rearrangement, you need the epoxide for ketone.
We'll soon find out if I'm a chemist or not!
(Title on BackOrder)
05-07-02 06:31
No 305654
Would there be any advantage to using sodium percarbonate to buffer the oxone instead of bicarbonate? Percarbonate releases the carbon dioxide at a MUCH slower rate than bicarbonate does, and it also might provide a means to recreate the persulfate, as sodium percarbonate has been used for creating other peracids.
(Hive Addict)
05-07-02 08:31
No 305699
How would one calculate the ammount of newly formed peracid ,by the percarbonate, to be used in relation to alkene. do you have any links for creating peracids from percarbonate?
VL_
(Title on BackOrder)
05-08-02 00:05
No 305926
most of the references I found for using percarbonates for forming epoxides used a different oxidizer as well, and the sources they listed as having success with just percarbonate were either Japanese or Brazilian journals that I couldn't find online or at school. I would say to calculate the amount of sodium percarbonate needed to buffer the oxone, and not worry about the peroxide calculations. this would add excess H2O2 to the reaction, but I don't think it would degrade the alkene.
(Ubiquitous Precursor Medal Winner)
05-08-02 01:54
No 305960
This OTC biz is wide open for experiment. Joe, the academics aren't going to tell us everything we might like to know. In my backwater, the health food & herb stores don't stock peroxide, the beverage distributors don't carry dry ice, etc., so some of my undocumented experiments are forced by necessity. I've found that the perborate like that used in xxxxxox non-chlorine dry bleach forms peroxides. It has a bit of built-in basic buffer, as does the percarbonate of oxx-clean, and both have water of crystallization (which is generally negligible). Your idea of using percarbonate for buffering and moderating the oxone rxn sounds useful to me, particularly if you count in the extra equivalent of sodium carbonate oxx-clean has off the shelf. Ain't no stopping us now.
I expect to run a rxn which uses peroxybenzoic acid (replacing the -COOOH with -Br, by CuBr2, to give bromobenzene) without recourse to any published synth details. I can make peroxyacids, easy as falling off a log. I'd just feel a bit more snuggly & comfy about the whole deal, if anybody could show me a link which has a sensible review on the actual explosion hazards of peracids.
a half a pints a half a pound a half a world a half a round
Sidearm n. Flask neck tube.
(Daddy)
05-08-02 08:44
No 306109
(Rated as: excellent)
As you prolly know, peracetic and performic acid in PURE form should never be heated above 110°C, that's why in the 15% H2SO4 hydrolisis step in the performic method it is adviced to use a waterbath, which can't go higher then 100°C by nature, and not use an oilbath, which accidently could be overheated. And the temp is adviced as not exceeding 80°C, for 2 to 3 hours.
Don't forget we work with diluted forms of peracids.
Links:
Perbenzoic acid and performic acid are mentioned as :
--- 3. Dangerous – When exposed to heat or flame may explode or is spontaneously flammable in air. In this link: http://www.engr.usask.ca/dept/cen/safety
Sadly there are no more details to gather on that page, but you all should read this page and look for chemicals you already use or plan to use. It's better to read it before using them.
Using the Edit/Find(On this page) function of IE while filling in - per - will quickly give you an impression which peroxides or other per's are dangerous.
So we got interested to find a more detailed description of the dangers you asked for:
http://www.engr.usask.ca/dept/cen/safety
---List of Some Incompatible Chemicals
---Substances in the right hand column should be stored and handled so they cannot possibly accidentally contact corresponding substances in the left hand column.---
(Very handy and should be read by everyone here.)
http://www.engr.usask.ca/dept/cen/safety
In there I found this, amongst a heap of other good advice which can safe your life:
Listed below are a few simple, but important reminders of precautions that should be considered in the routine handling of reagents.
-Before undertaking any chemical reaction always try to assess the hazards that may arise.
-Know the locations of safety showers, eye washes and the safety air packs and know how to use them.
-Keep reagent containers clean on the outside to protect your hands; use rubber or plastic gloves when appropriate.
-Be sure rubber gloves are clean on the inside before using; cleanse or decontaminate gloves regularly.
-Lab coats and closed-toed shoes should be worn to minimize hazards from splashes and spills.
-Avoid prolonged contact of chemicals with skin; wash hands and face frequently; be sure laboratory clothing is cleaned regularly.
-If water in not the appropriate washing agent, or antidote, procure proper first aid supplies before starting work.
-Avoid inadvertent contamination by not returning unused portions of reagents to stock bottles; stoppers should be held while pouring.
-Experiments involving toxic and corrosive vapours should be carried out in fume hoods. In general when working with small quantities of such materials the hood exhaust volume is sufficient to prevent an atmospheric pollution problem above and outside the building. When large scale operations are carried out in the fume hoods which evolve large amounts of either flammable, corrosive, or toxic vapours these vapours should not be simply vented to the outside but should be treated to destroy the harmful effects and thereby prevent atmospheric pollution outside the building.
-Condense flammable vapours and then dispose of the condensate. Other materials can be absorbed in an appropriate chemical solution.
-Never test chemical by taste.
-Smell cautiously - sniff (never inhale).
-Use a safety pipet filler, (pipeting by mouth is dangerous).
-Cool sealed vials of chemicals below the boiling point of the substance contained therein before breaking seal. Cool gradually, first in ice water, then CO2 etc., to avoid temperature shock to the glass vial and a possible explosion.
-Add concentrated chemicals to water (never vice versa).
-Low flash point liquids should be stored in safety cans.
-Limit quantities of solvents in glass bottles to one gallon.
-Keep flammable solvents such as benzene, ether, etc., away from hot plates and flames.
-Use care in transporting chemicals. The transporting of acids, liquids and hazardous solids to and from Stores is to be done using a pail or other carrier to retain the material if breakage occurs. This is to be strictly enforced by the Stores personnel.
-Use caution in working with mercury. The equilibrium concentration of Hg vapour over liquid mercury at room temperature is approximately 20 times the threshold toxic limit.
-Clean up spills of mercury and other chemicals promptly. (See SP-4 for cleanup procedure for mercury spills; see The Handbook on Laboratory Safety (located in the Thorvaldson Library for the method of cleanup of other chemicals).
PEROXIDES
-Are a frequent cause of laboratory explosions.
-Common solvents that peroxidize easily include:
-Ethers – dioxane, tetrahydrofuran, ethylene glycol dimethyl ether (glyme), diethylene glycol dimethyl ether (diglyme), diethyl ether, diisopropyl ether;
-Alcohols – some secondary alcohols, for example, isoprophyl alcohol;
-Hydrocarbons – cyclohexene, also other olefins; tetralin, decalin, branched-chained saturated hydrocarbons, alkyl substituted cycloaliphatics.
-Since peroxide explosions occur most frequently during distillation they should be carried out behind shields.
-Such materials should not be stored over long periods of time because peroxides form readily in poorly closed containers or even in well closed containers if there is air space above the solvent.
-Solvents should always be tested for peroxide content before using.
-Text methods and procedures for removing peroxides are described in The Handbook on Laboratory Safety (LT: a pinch of ferrous salt like ferrous chloride).
PERCHLORIC ACID
-Do not use perchloric acid on wooden benches or tables.
-Keep the perchloric acid bottles on glass or ceramic trays having enough volume to hold all the acid in case the bottle breaks.
-Discoloured acid (contaminated) should be disposed of immediately.
-Acids should be diluted prior to being returned to Stores for disposal.
-Operations in which the acid is heated to fuming are forbidden in ordinary hoods. An acceptable fume hood for this operation LT: should be specially build, including an explosion shield.
Am still searching for specific data on peracids, will return soon. LT/
WISDOMwillWIN
(Daddy)
05-08-02 09:45
No 306128
(Rated as: excellent)
http://www.engr.usask.ca/dept/cen/safety
- - - - - - - - - - - - - - - - - - - -
http://www.glasgow.ac.uk/seps/coshhbook.
Flammable Chemical Hazards Serious hazards can arise from the ease with which some common chemicals. particularly liquids, can be ignited. Flammable liquids present a special hazard since they are easily ignited, difficult to extinguish and burn with great rapidity. The more volatile liquids liberate heat up to ten times faster than wood, and their vapours form explosive mixtures in air. Some substances contain their own supply of oxygen and will burn in the absence of air, others are susceptible to spontaneous heating and others may react violently with other materials including water.
The important parameters of a flammable liquid are:
The flashpoint of a material is the lowest temperature at which sufficient vapour is given off to form an ignitable mixture with air (in the standard test apparatus employed). The lower the flashpoint, the more hazardous the material. Some extremely flammable liquids have flashpoints below --30<so>sC.
The lower and upper explosive limit ---- They are the minimum or maximum concentration of the substance in air below the mixture is too lean to burn, and above which it is too rich. For some materials, the range between these limits is 10-80%.
Safety Measures with Flammable ChemicaIs
No smoking.
Restrict quantities of flammable material to immediate requirements. In any case, not more than 50 litres may be stored in the laboratory, or workshop.
Confine the liquids ---- Flammable liquids in closed containers represent only a moderate hazard. In non-vapourtight apparatus, vapour will escape providing an easily ignitable fuel supply.
Eliminate ignition sources e.g. open flame, electrical equipment, hot surfaces, sparks and static electricity. Heat only by steam or water bath.
Ventilate to prevent accumulation of explosive mixtures --- The preferred safety measure is to use completely enclosed equipment. Where this is not practicable, extract ventilation must be provided to keep the concentration of flammable vapour below 25% of its lower explosive limit.
Fire fighting equipment suitable for the work must be immediately available.
Do not pour flammable chemicals down the drain.
Highly Reactive Chemicals When we talk of a routine chemical reaction, we imply a safe reaction; safe because the reaction rate is relatively slow or easily controlled. Highly reactive chemicals, however, can lead to reactions that differ from the routine (i.e. safe) in the rate at which they progress. The three types of violent decomposition are deflagration, explosion and detonation. The first two are more likely to occur in the laboratory following combustion of a flammable vapour or gas. In a small unconfined volume of fuel/air mixture, ignition will cause a deflagration to occur. People nearby may suffer minor injury but material damage will be minimal. This is because there is no significant pressure effect. There is, however, a volume effect and larger scale incidents of this type can be very destructive.
The effect of explosions under conditions of confinement can be serious. If the confinement is close and the fuel/air mixture is nearly stoicheiometric, an instantaneous pressure of several atmospheres can easily be produced. Such effects can destroy a laboratory and extreme precautions are necessary.
Explosions may also occur if a reaction accelerates out of control and to the point where the containing vessel fails and/or the vaporised contents reach their autoignition temperature. Fire will then definitely occur but explosion may not.
Many of the underlying causes of laboratory incidents which have involved the above effects stem from a lack of appreciation of the effects of simple physicochemical factors upon the reaction kinetics. Probably the most important of these govern the relationship of reaction rate with concentration, and with the rise in temperature during the reaction. Another factor which determines the course of a reaction is the overall elemental composition of the system. Most reactive chemical incidents have complex oxidation systems, and especially in organic systems the oxygen balance is an important consideration.
Oxygen balance is the difference between the oxygen content of a compound or mixture, and the oxygen which would be required to oxidise fully the carbon, hydrogen and other oxidisable elements present to carbon dioxide, water etc. If there is a deficiency of oxygen, the balance is negative and if a surplus, positive. Oxygen balance is expressed as a weight percentage with the appropriate sign. If the oxygen content of a compound approaches that necessary to oxidise the other elements present to their lowest valency state, then the stability of that compound is doubtful. (The exceptions are that nitrogen is excluded and is usually liberated as a gaseous element and halogen will go to halide if a metal or hydrogen is present. Sulphur, if present, counts as 2 atoms of oxygen). This generalisation is related to the fact that most high explosives have well below zero oxygen balance. Moreover, the presence of a fuel or reductant will increase the potential energy release.
Compounds with unusually high proportions of nitrogen and nitrogen-nitrogen bonds are also suspect. Hydrazine (87.4% nitrogen) and hydrogen azide (97.6%) are both explosively unstable, but ammonia (82.2%) is not.
In practical terms, the margin between potential and actual hazard depends on the activation energy for decomposition. Performic acid is treacherously unstable (low activation energy). TNT on the other hand is relatively stable and will not detonate when burned, but requires a powerful initiating explosive (detonator) to trigger explosive decomposition.
8.4 Toxic Dusts The danger of poisoning by inhalation or absorption through the skin is obvious when the substance is a liquid or gas. With solids, the danger often comes from breathing dust, ingestion or from powder lodged under finger nails. Quite large particles can travel deep into the lungs by inhalation, there to cause damage perhaps many years afterwards. Many dusts are quite inert but this does not mean that they are non-toxic, as they may accumulate in the body and ultimately impair lung function. Other dusts are toxic by inhalation in exactly the same way as other inhaled gases or vapours. These are usually metal compounds such as chromates or lead compounds. Others may cause allergies such as asthma or eczema. The effects produced may vary from person to person.
Perhaps the best known hazards from dust are from the fibrogenic dusts such as silica and asbestos. Inhalation of these dusts over extended periods can lead to degenerative fibrotic diseases of the lung and in the case of asbestos, there is an increased risk of cancer (especially if you are a smoker!).
8.6 Carcinogens, Mutagens and Teratogens.
Space precludes a detailed discussion of all the ramifications of this difficult and emotionally charged topic. The distinction between a carcinogen, a mutagen or a teratogen is perhaps of academic interest and the three can be considered together as being elements of genetic or reproductive toxicology.
At the time of writing, the Health and Safety Executive considers 23 substances or processes as having carcinogenic potential in man. However, the International Agency for Research on Cancer has published a list of 54 chemicals which they consider to pose a carcinogenic risk and the National Institute of Occupational Safety and Health (US) has published a list of 1,500 substances which they consider to be potential carcinogens. These vast numerical differences are a reflection of the political, legal, economic and scientific complexities which beset any rational discussion of chemical carcinogenesis.
A sense of proportion but not complacency is in order. All of us are exposed to chemicals throughout the day, either at work or at home or at play. While it is true that some chemicals used in industry have been responsible for well-publicised tragedies, it remains true that the single most widespread cause of cancer in western society is our use of tobacco.
Similarly, an increasing number of chemicals are becoming suspected of damaging human potential to reproduce. Such chemicals may interfere with the individual's capacity to initiate conception or may subsequently interfere with the safe development and delivery of the foetus. Both men and women as well as their offspring are at risk from exposure to these chemicals which obviously need to be handled with extreme care. Much the same difficulties beset a discussion of mutagens and teratogens as were described above for carcinogenic chemicals, so publication of a definitive list is impossible. This should serve to underline the need to be careful with handling chemicals at all times especially those with which we are unfamiliar or which have not yet been tested for carcinogenic potential.
2 Reference Books
There is a wide choice of reference books on hazardous substances any one of which may meet the requirements of smaller users.
Read the link(near bottom).
- - - - - - - - - - - - - - -
More to come, LT/
WISDOMwillWIN
(Stranger)
05-08-02 09:58
No 306134
Toxic dusts like fuckin' Sodium Metabisulphite !? Holy shit that stuff is bad to breath, like scratchin' from the inside out bad! Wear a gas mask or go outside when using alot of this stuff even digested in water, it's harshly sick stuff. And isn't this stuff sprinkled on salad bars as a preservative to keep the lettuce all fresh "lookin'". LOL It must be harshly buffed or banged with something to make it like .0001 % meta. ??Cough
"Taking risks are part of laboratory science."
- the Green Goblin
(Daddy)
05-08-02 10:14
No 306139
http://www.conncoll.edu/offices/envhealt
Material Safety Data Sheet Databases, a LOT of them, many links!
http://camel2.conncoll.edu/offices/envhe
What is a Material Safety Data Sheet?
WISDOMwillWIN
(Ubiquitous Precursor Medal Winner)
05-08-02 15:02
No 306228
LaBTop, thanks half a million. I have had some hints, that "safety first" means me too. I hate to feel stupid, but it's even worse to feel hurt and stupid. To get the stupid part of me under control, I am now insisting "use the gloves", "use the funnel", "get the goggles on" when it's needed. When I do any oxidation that I've no procedure details for, there's a cold water dish at hand in case of reaction-rate surprises. Paper towels and a real towel are in arm's reach at all times when glass is hot. My breathing mask is a joke, but it gets some use anyway. The fume hood's still under construction, but there's also a glove box in the planning stage; meanwhile there's a breezy back yard. Fire extinguishers are kept in place. Sometimes I think I'm turning sane.
This forcing myself to caution has even extended to trying to use big enough glass, and trying to use enough solvent for the reaction. Well, at least it's starting to. I still hate putting water into almost any reaction, and usually skimp on the amount of water used, beecause getting water out of things uses huge amounts of time. But with things I know are sketchy, I remember pretty well to use enough solvent. This includes things with too much oxygen for stability, peroxides, and little molecules with lots of nitrogen. Even feeling hurt and stupid, doesn't feel as bad as feeling hurt and stupid and blown up.
So to produce my peroxy acid I need, I'll use excess solvent and not overheat. I won't boil anything to dryness. I seldom boil anything literally to dryness any more anyway. I am very tempted to use DMSO to stay away from using water, though I know DMSO is an oxygen carrier and can serve as an oxidant. (I have bought bottles of DMSO carrying a warning label saying that it can form explosive compounds with some acid chlorides.) I'll still have to decide on a solvent system to use, and much as I hate it, it'll probably include water. Acetone is another oxygen carrier, which can also form an explosive derivative. I'll have to think deeper about the solvent system, for emphasis on safety instead of operator convenience. Everything stays wet at all times, and peroxyacids will not be highly concentrated by heating. This indicates solvent extraction in the workup, but that presents the objection that separation of peroxyacid from unreacted acid is tough. Why do experimenters have to think so hard, when it's so much easier to say aw fuck it and start mixing things.
a half a pints a half a pound a half a world a half a round
Sidearm n. Flask neck tube.