Kahlil27
Harmless
Posts: 2
Registered: 16-11-2006
Location: Not telling:)
Member Is Offline
Mood: flatline
|
|
BH3/THF
Whats the easiest way for me to make a BH3/THF solution??
|
|
|
matei
Hazard to Others
Posts: 205
Registered: 16-9-2006
Member Is Offline
Mood: No Mood
|
|
From boron trifluoride etherate and sodium borohydride. See Vogel's Textbook of Practical Organic Chemistry 5'th Edition page 418 for the exact
procedure. Diborane can be generated externally or in situ.
|
|
|
Maya
Hazard to Others
Posts: 263
Registered: 3-10-2006
Location: Mercury
Member Is Offline
Mood: molten
|
|
Why is this in the ORGANIC Chemistry section? Shouldn't this be in the INORGANIC?
anyways , p786, p219 Brauer's 1963 HPIC
Boron Trifluoride Etherate
BF,O(C2H5)2
BF, + O(C2H5)2 = BF3-O(C2H5)o
67.8 74.1 141.9
Two moles (135.6 g.) of BF3 are generated as described on p.
219. It is then introduced into a dry one-liter flask containing 148
g. of diethyl ether. Alternately, the BF3 may be frozen at liquid
nitrogen temperature and added as a solid. The flask is cooled in
ice-salt mixture and access of atmospheric moisture is prevented
by closing off the flask with a CaCl3 tube. The stream of BF3 should
not be too fast because some of it will not be taken up by the ether
in that case. After the end of the reaction a condenser is connected
to the flask and the BF3- O(C3Hs)s distilled off at 125°C into a receiver,
preferably at reduced pressure. The etherate distills
readily at 38°C (6 mm.).
//////////////////////////////
Boron Trifluoride
BF3
I- KBF4 + 2 B2O3 = BF3 + KF • B4O6
125.92 139.28 67.82 197.38
A mixture of 80 g. of dried or, preferably, melted KBF4 and
30 g. of B2O3 is heated to about 600°C in an inclined iron tube (40 cm. long, 3 cm. diameter), which is sealed at one end. The other end of the iron
tube is closed by a flange sealed with a copper gasket. An appr. 10-mm. -diameter iron tube is welded into an glass wool, which acts as a dust filter.
The drying tube is in turn joined to a quartz or glass trap cooled in liquid nitrogen. The apparatus ends in a drying tube filled with freshly dried
KF. The yield is 17 g. of BF3. This can be purified by repeated fractional distillation.
II. 6 NaBF4 + B2O3 + 6 H2SO4 = 8 BF3
658.92 69.64 588.40 542.56
6 NaHSO, + 3 H2O
720.36 54.04
A mixture of 300 g. of NaBF4,50 g. of B2O3 and 300 ml. of concentrated
H2SO4 is carefully heated in a one-liter flask provided
with a ground-glass joint (see Fig. 133) until gas evolution starts.
Only then can more heat be applied. The exit gas passes through
a condenser, then through an absorption tube filled with B2O3
which has been interspaced with glass wool, and finally it is condensed
in a trap at —196°C. A KF drying tube is placed at the end
of the system in order to exclude moisture.
\_
V
liq. N2
Fig. 133. Preparation of boron
trifluoride.
The advantage of this method of preparation is that the residues
are water soluble and the reaction vessel can be easily cleaned.
According to Ryss and Polyakova, the best BF3 yield (80%) is
obtained at 180°C with 105.9% sulfuric acid (oleum) in a 200%
excess.
III. H3BO3 + 3 HSO3F = BF3 + 3 H2SO4
61.84 300.22 67.82 294.24
Concentrated HaSO4is placed in an iron reaction vessel, which
has one gas and two addition nozzles on top and one outlet nozzle
(with a valve) at the bottom. A solution of 20-25% boric acid in
concentrated H2SO4 and HSO3F is added at 85 to 135°C. The BF3
is slowly liberated. The H2SO4 which accumulates may be removed
from time to time at the bottom and may be used to dissolve the
boric acid.
Further preparative methods: IV. Thermal decomposition of
diazonium fluoroborates [G. Balz and G. Schiemann, Ber. dtsch.
chem Ges. 60, 1186 (1927)].
V. A mixture of 40 g. of KBF4, 8 g. of BSQB and 120 ml. of
concentrated sulfuric acid is heated to 270°C on a sand bath in a
300-ml. flask equipped with ground-glass joints [P. Baumgarten
and H. Henning. Ber. dtsch. chem. Ges. 72., 1747 (1931)].
The older method for preparing BF3 starting with CaF3 is not
recommended, since the yields are low and the product is contaminated
with SiF4.
The product is stored in glass containers over Hg or in steel
cylinders.
Derivatives:
PROPERTIES:
BF3
BF3
BF3
• (OCgHg
• NHg P .
• 2H,Op
HCBFa(OH)J
n-C4HaBFgp
)sP. 7S
785
. 784
p. 784
. 802
Colorless, asphyxiating gas, fumes in moist air, thermally
very stable.
M.p. —128°C,b.p. — 101°C;tcr — 12.25°C;pc r50.2atm. gage;
d (liq.) (—128°C) 1.769; d (solid) (—150°C) 1.87.
Hydrolyzes in water to give H3BQ3 and HBF4. The gas attacks
rubber. Rubber tubing and stoppers should therefore be avoided in
apparatus used in its preparation.
REFERENCES:
I. W. Hellriegel. Ber. dtsch. chem. Ges. 70, 689 (1937).
II. H. S. Booth and K. S. Willson. J. Amer. Chem. Soc. 57, 2273
(1935); I.G. Ryss and Y.M. Polyakova. Zh. Obshch. Khim.
19 (81), 1596 (1949) (Chem. Zentr. 5£. II. 1329).
[Edited on 17-11-2006 by Maya]
[Edited on 17-11-2006 by Maya]
[Edited on 17-11-2006 by Maya]
|
|
|
matei
Hazard to Others
Posts: 205
Registered: 16-9-2006
Member Is Offline
Mood: No Mood
|
|
Maya, diborane is used in organic chemistry for hydroborations.
Boron trifluoride diethyl etherate can be purchased. Its preparation in a laboratory is not usually attempted (it doesn't worth the effort and BF3 gas
is very toxic; btw diborane is also very toxic and should be prepared and handeled in a fume hood).
|
|
|
Maya
Hazard to Others
Posts: 263
Registered: 3-10-2006
Location: Mercury
Member Is Offline
Mood: molten
|
|
did I mention that it also ignites spontaneously upon contact with air?
pretty nasty stuff, I was just answering the question , not saying he should actually try it and set him/herself on fire..........
|
|
|
The_Davster
A pnictogen
Posts: 2861
Registered: 18-11-2003
Member Is Offline
Mood: .
|
|
I am pretty sure diborane can be bubbled into THF to make this as well.
Diborane is available from the reaction of borohydride with iodine, and through several other methods.
|
|
|
Maya
Hazard to Others
Posts: 263
Registered: 3-10-2006
Location: Mercury
Member Is Offline
Mood: molten
|
|
okay, if one insists on spontaneous cumbustion , then the second part of this synth
would be to add a solution of sodium borohydride to boron triflouride-etherate and sweep the resulting diborane into THF with the aid of a nitrogen
gas stream
3 NaBH4 + 4BF3 = 4BH3 + 3 NaBF4
per Vogels 4th ed p 292
plse don't blow yourself up..........
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
