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How to make Sodium tetraphenylborate

Jun. 20, 2019
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Sodium tetraphenylborate is a very important chemical used primarily for the detection of potassium, such as the analysis of potassium-containing fertilizers, potassium in the blood, and so on. Sodium tetraphenylborate can be used to prepare and separate some organometallic complexes in organic synthesis applications.


Therefore, if you need to test potassium or perform organic synthesis, you will need the following Sodium tetraphenylborate preparation steps.


method 1

The Grignard reagent is first synthesized with magnesium chips, benzene bromide and diethyl ether solutions and iodine tablets, and the content thereof is generally from about 39% to about 43%.

Then, the Grignard reagent is reacted with trimethyl borate, hydrolyzed, extracted with diethyl ether, and filtered.

The filtrate was extracted with chloroform, and a salt was added to the extract to form a white precipitate (sodium tetraphenylborate).

Further, it was extracted with acetone, and the salt was filtered off. The filtrate was concentrated under reduced pressure at room temperature, crystallized, recrystallized from acetone, and dried at 30-40 ° C.

A fine product of sodium tetraphenylborate is obtained.


Chemical equation

NaBF4 + 4PhMgBr → 2MgBr2 + 2MgF2 + NaBPh4


Method 2

A magnesium phenylmagnesium bromide solution is prepared by dissolving magnesium metal and bromobenzene in anhydrous ether.

A solution of sodium tetrafluoroborate and diethyl ether was added.

The reaction mixture was placed on a water bath under vacuum and boiled.

Add decolorization with activated carbon, filter, add sodium chloride, and precipitate sodium tetraphenylborate.


Method 3

Magnesium chips were filled into the reaction tube and then immersed in purified anhydrous ether.

Iodine was added as an initiator and slowly heated to reflux with diethyl ether.

Then, a solution of bromobenzene in diethyl ether was slowly added dropwise.

The drip acceleration is controlled to keep the liquid level in the tube boiling. When the phenyl bromide is formed, it can be discharged while being added dropwise.

When magnesium is consumed in half, it should be replenished in time.

The resulting phenylbromomagnesium was diluted with anhydrous diethyl ether, and while stirring, a trimethyl borate anhydrous ether solution was slowly added, and the temperature was controlled at about 34 °C.

After completion of the reaction, the mixture was allowed to stand, and the upper layer of diethyl ether was separated, and the lower layer solution was at or below 10 °C.

A small amount was added to the aqueous sodium carbonate solution in portions, and after the addition was completed, stirring was continued for half an hour.

After standing, the ether layer was separated.

It was extracted with diethyl ether to a pH of 8 to 9, and the extracts were combined.

Activated carbon was added, heated and stirred, filtered while hot, and distilled under reduced pressure.

Ether, methanol, and water were distilled off in this order, cooled, and filtered.

The filtrate was dehydrated by adding water and activated carbon, distilled under reduced pressure until the distillate was clarified, cooled, and decolorized by filtration, and the filtrate had a pH of not less than 8.

The crude sodium tetraphenylborate was mixed into a solution and then activated carbon was added and stirred for 4 hours.

The mixture was decolorized by filtration, and the filtrate was concentrated by heating until a small amount of salt was precipitated, maintaining the temperature at 90 °C.

After stirring, a saturated saline solution of pH=8 to 9 at 90 ° C was added for salting out, and the mixture was filtered while hot, and the crystal was dried at 60 ° C.

The obtained sodium tetraphenylborate was added in small portions to acetone below 5 °C.

After treatment with activated carbon, acetone was recovered under reduced pressure until the residue was cloudy, and then decompressed to dryness at room temperature.

It is filtered, washed with anhydrous diethyl ether, and dried to give a fine sodium tetraphenylborate.


The above is the three preparation methods of sodium tetraphenylborate, if you have other method for make Sodium tetraphenylboron, welcome to contact us! I will add your method on this post!


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