Shopping on line can be easy, simple and save you lots of money. It can also take a lot of your time, frustrate you, and result in unwanted purchases. Now the same can be said for regular high street shopping, but with the vast opportunity presented by the Internet it will pay you to spend a few minutes reading this and understanding how to better optimize your Phosphorus Tribromide shopping experience:
1. Compare - without doubt the biggest advantage that the Phosphorus Tribromide offers shoppers today is the ability to compare thousands of Phosphorus Tribromide at a time. This is a great thing, but not necessarily all the time! Too much can be daunting at times so take advantage of the great comparison sites and where possible let them do the hard work for you.
2. Research - if it has been said it will be on the internet. Ignorance is no longer a justifiable reason for buying the wrong thing. Take the time to research in detail everything that you could possible want to know about
3. Testimonials - don't know anybody that has bought a Phosphorus Tribromide? Wrong! If the Phosphorus Tribromide is good the internet will let you know. Use the Internet as a friend and get testimonials before you buy.
4. Questions - Got a question about Phosphorus Tribromide then search the Forums, FAQ's, Blogs etc. Don't be afraid to ask .....
5. Reputation - Never heard of the company selling Phosphorus Tribromide? Don't worry, no reason why you should know every company in the world, but you know someone that does! Use the internet to find out what people are saying about Phosphorus Tribromide and build up a picture of their reputation for sales, returns, customer service, delivery etc.
6. Returns - still worried that even after all of the above your Phosphorus Tribromide wont be what you want? Check out the returns policy. There is so much competition now that someone, somewhere is bound to offer the terms that you are comfortable with.
7. Feedback - happy with your Phosphorus Tribromide then let people know, after all you are depending on others people input in your buying decision, so why not give a little back.
8. Security - check for the yellow padlock on the Phosphorus Tribromide site before you buy, and the s after http:/ /i.e. https:// = a secure site
9. Contact - got a question about Phosphorus Tribromide, or want to leave a comment then check out the sites contact page. Reputable companies have them and respond.
10. Payment - ready to pay for your Phosphorus Tribromide, then use your credit card or PayPal! Be aware of companies that don't accept them, there may be genuine reasons but given the huge amount of choice you have when buying online there is no reason at all not to buy via credit card or PayPal.
{{Chembox new| Name = Phosphorus tribromide| ImageFile = Phosphorus-tribromide-2D-dimensions.png| ImageName = Phosphorus tribromide| ImageFile1 = Phosphorus-tribromide-3D-vdW.png| ImageName1 = Phosphorus tribromide| IUPACName = phosphorus tribromide| OtherNames = phosphorus(III) bromide
phosphorous bromide
tribromophosphine| Section1 = {{Chembox Identifiers| CASNo = 7789-60-8| RTECS = TH4460000 -->
| Section2 = {{Chembox Properties| Formula = PBr3| MolarMass = 270.70 g/mol| Appearance = clear, colourless liquid| Density = 2.852 g/cm3, liquid| Solubility = rapid hydrolysis| MeltingPt = -41.5 °C (231.7 K)| BoilingPt = 173.2 °C (446.4 K)| Viscosity = -->
| Section3 = {{Chembox Structure| MolShape = trigonal pyramidal| Dipole = -->
| Section7 = {{Chembox Hazards| MainHazards = corrosive, toxic, reactive
with water and alcohols| FlashPt =| RPhrases = 14, 34, 37| SPhrases = 25, 45 -->
| Section8 = {{Chembox Related| OtherAnions = phosphorus trifluoride
phosphorus trichloride
phosphorus triiodide
[arsenic tribromideantimony tribromide
[phosphorus oxybromide -->
-->
Phosphorus tribromide is a colourless liquid with the formula Phosphorus
Bromine3. It fumes in air due to
hydrolysis and has a penetrating odour. It is widely used in the laboratory for the conversion of
alcohols to alkyl halides.
Chemical properties
Phosphorus tribromide, like
Phosphorus trichloride and Phosphorus trifluoride, has both properties of a
Lewis base and a Lewis acid. For example, with a Lewis acid such as boron tribromide it forms stable 1:1 adducts such as Br3B-PBr3. At the same time PBr3 can react as an electrophile or Lewis acid in many of its reactions, for example with
amines.
The most important reaction of PBr3 is with
alcohols, where it replaces an
hydroxyl group with a bromine atom to produce an
Alkyl halide. Note that all three bromines can be transferred.
PBr3 + 3 Alcohol → 3
Alkyl halide +
Phosphorous acid
The mechanism (shown for a primary alcohol) involves initial activation of the alcohol oxygen by the electrophilic phosphorus (to form a good leaving group), followed by an
SN2 reaction at the alcohol carbon.
Because of the SN2 substitution step, the reaction generally works well for Alcohol#Primary, secondary and tertiary alcoholss, but fails for tertiary alcohols. If the reacting carbon centre is
chirality (chemistry), the reaction usually occurs with Stereochemistry at the alcohol carbon, as is usual with an SN2 reaction.
In a similar reaction, PBr3 also converts
carboxylic acids to Acyl halides.
PBr3 + 3 Carboxylic acid → 3
Acyl halide +
Phosphorous acid
PBr3 is a reasonably strong Redox, and the oxidation of PBr3 with oxygen gas is more vigorous than seen with PCl3. It gives an explosive reaction that forms
Phosphorus pentoxide and
bromine.
Preparation
PBr3 is prepared by treating phosphorus with bromine, using PBr3 itself as the solvent (white phosphorus is soluble in PBr3). An excess of phosphorus is used in order to prevent formation of PBr5.
Phosphorus + 6 Bromine → 4 PBr3
Uses
The main use for phosphorus tribromide is for conversion of primary or secondary
alcohols to alkyl halides, as described #Chemical properties. PBr3 usually gives higher yields than
hydrobromic acid, and it avoids problems of
carbocation rearrangement- for example even
neopentyl bromide can be made from the alcohol in 60% yield.
Another use for PBr3 is as a catalyst for the α-bromination of
carboxylic acids. Although acyl bromides are rarely made in comparison with acyl chlorides, they are used as intermediates in Hell-Volhard-Zelinsky halogenation. Initially PBr3 reacts with the carboxylic acid to form the acyl bromide, which is more reactive towards bromination. The overall process can be represented as
On a commercial scale, phosphorus tribromide is used in the manufacture of [pharmaceuticals such as alprazolam,
methohexital and
fenoprofen. It is also a potent fire suppression agent marketed under the name PhostrEx.
Precautions
PBr3 evolves corrosive HBr, is toxic, and reacts violently with water and alcohols.
In reactions that produce
phosphorous acid as a by-product, when working up by distillation be aware that this can decompose above about 160 °C to give phosphine which can cause explosions in contact with air.
References
N. N. Greenwood, A. Earnshaw, Chemistry of the Elements, 2nd ed., Butterworth-Heinemann, Oxford, UK, 1997.
Handbook of Chemistry and Physics, 71st edition, CRC Press, Ann Arbor, Michigan, 1990.
J. March, Advanced Organic Chemistry, 4th ed., p. 723, Wiley, New York, 1992.
The Merck Index, 7th edition, Merck & Co, Rahway, New Jersey, USA, 1960.
R. R. Holmes, Journal of Inorganic and Nuclear Chemistry 12, 266-275 (1960).
L. G. Wade, Jr., Organic Chemistry, 6th ed., p. 477, Pearson/Prentice Hall, Upper Saddle River, New Jersey, USA, 2005.
George C. Harrison, H. Diehl, in Organic Syntheses Collective Volume 3, p 370, Wiley, New York, 1955.
L. G. Wade, Jr., Organic Chemistry, 6th ed., p. 1051, Pearson/Prentice Hall, Upper Saddle River, New Jersey, USA, 2005.
{{Chembox new| Name = Phosphorus tribromide| ImageFile = Phosphorus-tribromide-2D-dimensions.png| ImageName = Phosphorus tribromide| ImageFile1 = Phosphorus-tribromide-3D-vdW.png| ImageName1 = Phosphorus tribromide| IUPACName = phosphorus tribromide| OtherNames = phosphorus(III) bromide
phosphorous bromide
tribromophosphine| Section1 = {{Chembox Identifiers| CASNo = 7789-60-8| RTECS = TH4460000 -->
| Section2 = {{Chembox Properties| Formula = PBr3| MolarMass = 270.70 g/mol| Appearance = clear, colourless liquid| Density = 2.852 g/cm3, liquid| Solubility = rapid hydrolysis| MeltingPt = -41.5 °C (231.7 K)| BoilingPt = 173.2 °C (446.4 K)| Viscosity = -->
| Section3 = {{Chembox Structure| MolShape = trigonal pyramidal| Dipole = -->
| Section7 = {{Chembox Hazards| MainHazards = corrosive, toxic, reactive
with water and alcohols| FlashPt =| RPhrases = 14, 34, 37| SPhrases = 25, 45 -->
| Section8 = {{Chembox Related| OtherAnions = phosphorus trifluoride
phosphorus trichloridephosphorus triiodide
[arsenic tribromideantimony tribromide
[phosphorus oxybromide -->
-->
Phosphorus tribromide is a colourless liquid with the formula
PhosphorusBromine3. It fumes in air due to
hydrolysis and has a penetrating odour. It is widely used in the laboratory for the conversion of
alcohols to
alkyl halides.
Chemical properties
Phosphorus tribromide, like
Phosphorus trichloride and
Phosphorus trifluoride, has both properties of a
Lewis base and a Lewis acid. For example, with a Lewis acid such as
boron tribromide it forms stable 1:1 adducts such as Br3B-PBr3. At the same time PBr3 can react as an electrophile or Lewis acid in many of its reactions, for example with amines.
The most important reaction of PBr3 is with alcohols, where it replaces an hydroxyl group with a bromine atom to produce an
Alkyl halide. Note that all three bromines can be transferred.
PBr3 + 3 Alcohol → 3 Alkyl halide + Phosphorous acid
The mechanism (shown for a primary alcohol) involves initial activation of the alcohol oxygen by the electrophilic phosphorus (to form a good leaving group), followed by an
SN2 reaction at the alcohol carbon.
Because of the SN2 substitution step, the reaction generally works well for Alcohol#Primary, secondary and tertiary alcoholss, but fails for tertiary alcohols. If the reacting carbon centre is
chirality (chemistry), the reaction usually occurs with
Stereochemistry at the alcohol carbon, as is usual with an SN2 reaction.
In a similar reaction, PBr3 also converts
carboxylic acids to
Acyl halides.
PBr3 + 3
Carboxylic acid → 3 Acyl halide +
Phosphorous acid
PBr3 is a reasonably strong Redox, and the oxidation of PBr3 with
oxygen gas is more vigorous than seen with PCl3. It gives an explosive reaction that forms Phosphorus pentoxide and
bromine.
Preparation
PBr3 is prepared by treating
phosphorus with
bromine, using PBr3 itself as the solvent (white phosphorus is soluble in PBr3). An excess of phosphorus is used in order to prevent formation of PBr5.
Phosphorus + 6
Bromine → 4 PBr3
Uses
The main use for phosphorus tribromide is for conversion of primary or secondary
alcohols to alkyl halides, as described
#Chemical properties. PBr3 usually gives higher yields than hydrobromic acid, and it avoids problems of carbocation rearrangement- for example even neopentyl bromide can be made from the alcohol in 60% yield.
Another use for PBr3 is as a catalyst for the α-bromination of carboxylic acids. Although acyl bromides are rarely made in comparison with
acyl chlorides, they are used as intermediates in Hell-Volhard-Zelinsky halogenation. Initially PBr3 reacts with the carboxylic acid to form the acyl bromide, which is more reactive towards bromination. The overall process can be represented as
On a commercial scale, phosphorus tribromide is used in the manufacture of [pharmaceuticals such as alprazolam, methohexital and
fenoprofen. It is also a potent fire suppression agent marketed under the name PhostrEx.
Precautions
PBr3 evolves corrosive HBr, is toxic, and reacts violently with water and alcohols.
In reactions that produce
phosphorous acid as a by-product, when working up by distillation be aware that this can decompose above about 160 °C to give phosphine which can cause explosions in contact with air.
References
N. N. Greenwood, A. Earnshaw, Chemistry of the Elements, 2nd ed., Butterworth-Heinemann, Oxford, UK, 1997.
Handbook of Chemistry and Physics, 71st edition, CRC Press, Ann Arbor, Michigan, 1990.
J. March, Advanced Organic Chemistry, 4th ed., p. 723, Wiley, New York, 1992.
The Merck Index, 7th edition, Merck & Co, Rahway, New Jersey, USA, 1960.
R. R. Holmes, Journal of Inorganic and Nuclear Chemistry 12, 266-275 (1960).
L. G. Wade, Jr., Organic Chemistry, 6th ed., p. 477, Pearson/Prentice Hall, Upper Saddle River, New Jersey, USA, 2005.
George C. Harrison, H. Diehl, in Organic Syntheses Collective Volume 3, p 370, Wiley, New York, 1955.
L. G. Wade, Jr., Organic Chemistry, 6th ed., p. 1051, Pearson/Prentice Hall, Upper Saddle River, New Jersey, USA, 2005.
