2020-08-13

Copper(II) bromide from copper sulphate

 Reagents: 

1 gram CuSO4 * 5H2O (4 mmol, M= 250g/mole)

0.95 grams KBr (8 mmol, M= 119g/mole)

distilled water

acetone

 

Procedure: 

 1 gram of CuSO4 *5H2O (4 mmol) and 0.95 grams of  KBr (8 mmol) were dissolved in 15 ml of distilled water. Then 20 ml of acetone was added. The solution changed color - from blue/green to green, black and light blue.


Precipitate was filtered and washed 3 times with acetone. The solid on filter was pale blue. After first washing it changed color to dark green. After each of washings the color became lighter.




 

 



The filtrate had dark-green colour.

 

Extraction was repeated giving pale blue precipitate on filter and clean filtrate.

The precipitate here is mostly potassium sulphate and some copper(II) remainings

 


Combined extracts were evaporated to dryness. During evaporation formation of white crystals was observed. Finally, 0.7 grams of black product with some minor green impurities was isolated







Quick analysis showed that it is not the desired compund. CuBr2 is water-soluble and it's solutions are green. This compound creates white suspension. It also reacts with H2O2 giving brown color which could be metallic copper - CuBr2 should be converted to green Cu(OH)2


At least filter paper looks nice 30 minutes after the reaction

 


This reaction was performed to test if it is possible to get CuBr2 from mixed solvent system. CuSO4, K2SO4 and KBr and CuBr2 are soluble in water, but only CuBr2 is soluble in acetone. The procedure confirmed that CuBr2 can't be obtained from CuSO4 and CuBr2 by simple extraction from water and acetone. Instead of giving copper(II) bromide it yields some bromocopper complexes. 

CuBr2 is known oxidizing agents. It could oxidize acetone yielding Cu1+ ions.


2020-07-24

Bromoethane

Reagents: 

175g H2SO4 (~1.8 mole, 96ml)
72.6g ethanol 95% ( 1.5 mole, 92ml)
80g KBr (0.672 mole)
Na2CO3 5% solution
 water

 Procedure: 

Round bottom flask was charged with 96 ml of concentrated sulphuric acid (1.8 mole). Ethanol was added slowly to avoid boiling. After addition and cooling the mixture to room temperature 80 grams of KBr (0.672 mole) dissolved in 50 millilitres of water was added. Distillation setup was manteled - a beaker containing ice cold water was used as receiver. The end of receiver bend was submerged in water. Heating was provided and stopped when there were no signs of product distillation. Collected product was washed with 5% Na2CO3 solution and water.
Washed product was distilled again and fraction boiling between 35C and 40C was collected.



Theoretical yield (based on KBr) - 73.2 grams
Practical yield: 59.9 grams - 81.8%


2020-07-23

Iodic acid - HIO3

This one was a failed attempt to synthesize iodic acid from iodine and nitric acid

Reagents:

    50 grams  HNO3 (97.5%)
    10 grams I2
    
Procedure:

Round bottom flask equipped with reflux condenser and thermometer was charged with 50 grams of concentrated nitric acid. The acid was heated to 70 C. 10 grams of iodine was added in small portions. The temperature was set to 85 degrees for 45 minutes. After that the reaction mixture was cooled down and neutralized.

Notes:

It was unsuccessful attempt to synthesize HIO3. One of the products of this reaction was nitrogen dioxide and the amount of this noxious gas was so large that I wasn't sure if fume hood will handle it.
The next attempt will be performed in smaller scale.

Safety:

     nitric acid is corrosive and strong oxidizing  (latex and nitrile glove can burst into flames in contact             with nitric acid)

    iodine vapour is irritant and toxic

    NO2 is highly toxic and inhalation could be fatal. It's action has delayed onset and first symptoms may     be visible even after two days.

2020-07-20

Nitric acid

Reagents
 100g H2SO4 98% (1 mole)
  84.9g NaNO3 (1 mole)
  NaOH solution (trap)

Procedure:
250ml round bottom flask was charged with 84.9 grams of NaNO3 and 100 grams of concentrated sulphuric acid ``was added. Simple distillation setup with NaOH trap was mantled and reaction flask was heated.
The heating was stopped when the reaction mixture solidified.

The product received in receiver flask weight was 50.5g, volume 33.5ml and it's temperature was 15 C. 
From the density table we found that density of about 1.5075 was equivalent to concentration of 97.5%, so the yield is 49.24 grams of pure HNO3.

Reaction stoichiometry: H2SO4 + NaNO3 -> HNO3 + NaHSO4

Theoretical yield – 1 mole of HNO3 (63 grams)
Practical yield – 0.78 mole (49.24 grams) 78.16%

Notes:
During the distillation a brown gas was produced in reaction flask (NO2). The foaming was observed. Foaming was proportional to the heating. After cooling the reaction mixture the foaming decreased (in the future use larger flask). 


The product was yellow due to some NO2 was dissolved. There was no need to purify.
Such concentrated HNO3 is hard to store, it fumes a lot and it builds a pressure inside a bottle so it requires frequent venting.. It's fumes corrode standard laboratory blue caps.

Safety:
    sulphuric acid is corrosive
    nitric acid is corrosive and it's a strong oxidizer. Work without gloves (latex, nitrile), because they will burst into flames when spill occur

The trap presented here should be mantled differently using inverted funnel. This one is prone to suck-back and ruining the product.

2020-07-19

Bromine isolation


Today we will proceed with isolation of bromine. We will need it for further syntheses.

Reagents:
    52.4g  KBr (0.44 mole)
    43.2g H2SO4 98%  (0.44 mole, 24ml)
    50.5g H2O2 30% (0.44 mole, 45.5ml)
    80ml of distilled water
    H2SO4 98% for dehydration
    NaOH solution (trap)
    Na2 S2O3 solution

Procedure:
52.4 grams of KBr was dissolved in 80ml of distilled water and poured to 250ml 3-neck round bottom flask.  Simple distillation setup was mantled with a trap containing NaOH solution connected to the vacuum adapter. Then 43.2 grams of concentrated sulphuric acid were added slowly.

Addition funnel with pressure equalizer was mounted on one of the remaining necks and was charged with 50.5 grams of 30% hydrogen peroxide.The neck which was unused was closed by the stopcock.

Receiver flask was submerged in ice-cold water, ice-cold water was also running through the condenser.
Hydrogen peroxide was added drop-wise. During addition, the temperature in the flask raised so much, that external heating was not needed. This reaction is highly exothermic and pouring it fast is a recipe for huge problems. After the addition has completed heating mantle was enabled and distillation was continued until the content of reaction flask changed the colour to yellow.




During the distillation, another portion of concentrated sulphuric acid was prepared and cooled down in ice bath. After the distillation has completed, the acid was poured in separatory funnel, then the distillate was poured also. The content was shaken and after 5 minutes the bottom layer containing elementary, dehydrated bromine was collected to the beaker. Then it was pipetted to glass ampoule and sealed. The ampoule was placed in container secured with sodium thiosulphate in case of any leaks.



Stoichiometry of this reaction: 2KBr+2H2SO4+H2O2→Br2+2KHSO4 +2H2O

Theoretical yield – 0.22 mole of Br_2 (35.156 grams) – based on starting KBr
Practical yield – 0.115 mole (18.4 grams)

Notes: yield could be improved by providing better cooling. The amount of ice which were used for cooling the reaction flask and condenser water was too small and huge amount of bromine evaporated and was trapped in NaOH solution.

Safety:
    bromine is corrosive and toxic
    sulphuric acid, sodium hydroxide and hydrogen peroxide are corrosive
Inhalation of bromine vapours can be fatal – the procedure must be performed in fume hood or well-ventilated area with respirator. Storage of bromine is problematic. The only one reliable solution is sealed glass ampoule.
In case of any bromine spills it is necessary to have sodium thiosulphate solution prepared. It will neutralize elementary bromine to bromine anions which are non-toxic.
Dismantling the apparatus is easy. Bromine has strong vapour pressure and it need just few minutes to evaporate. After that the apparatus should be rinsed with sodium thiosulphate solution.