Chloroform Synthesis via the Haloform Reaction

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Chloroform Synthesis (Haloform Reaction)

Materials Required:

Serial No.​	Chemical Name​	Amount​	CAS Number​
1	Sodium Hydroxide (NaOH)	10g	1310-73-2
2	Sodium Hypochlorite (NaOCl)	200 mL	7681-52-9
3	Acetone (CH₃COCH₃)	10 mL	67-64-1
4	Distilled Water	10 mL + 100 mL	7732-18-5
5	Anhydrous Calcium Chloride (CaCl₂)	5g	10043-52-4

Glassware Required:

• 250 mL Beaker
• Stirring rod or magnetic stirrer
• Separation funnel
• 1000 mL Beaker
• Büchner funnel for filtration
• Graduated cylinder for precise liquid measurement
• Ice bath (to maintain reaction temperature)

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Step-by-Step Synthesis Process

Step 1: Prepare Sodium Hydroxide Solution

• Procedure:
  • Measure 10g of sodium hydroxide (NaOH) and dissolve it in 100 mL of distilled water in a 250 mL beaker.
  • Stir the mixture using a magnetic stirrer until completely dissolved.
  • Exothermic Reaction Warning: The dissolution of NaOH in water is exothermic, meaning heat will be generated, so it's important to allow the solution to cool to room temperature before proceeding to the next step.

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Step 2: Add Sodium Hypochlorite (Bleach)

• Procedure:
  • Carefully add 200 mL of sodium hypochlorite (bleach) to the prepared NaOH solution. Stir constantly to ensure uniform mixing.
  • This solution is the key for the haloform reaction, which occurs later when acetone is introduced.
  • Keep the mixture in an ice bath if necessary to avoid overheating as sodium hypochlorite decomposes.

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Step 3: Add Acetone (Initiating the Haloform Reaction)

• Procedure:
  • Slowly add 10 mL of acetone to the sodium hypochlorite-NaOH solution.
  • Stir the mixture continuously as the reaction begins. The haloform reaction starts here, where the acetone reacts with sodium hypochlorite to produce chloroform (CHCl₃) and sodium acetate.
  • This reaction is exothermic and can produce heat, so monitor the temperature closely. Maintain it below 17°C by placing the beaker in an ice bath to control the rate of reaction.

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Step 4: Stirring and Monitoring the Reaction

• Procedure:
  • Stir the mixture for 20-30 minutes while maintaining the temperature. The formation of chloroform will occur during this time, and the product will begin to precipitate as a heavier liquid layer at the bottom of the solution.
  • Continue stirring until the formation of chloroform is visually noticeable as a denser, clear liquid beneath the upper aqueous layer.

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Step 5: Separation of Chloroform

• Procedure:
  • Transfer the mixture into a separation funnel. Let it stand for about 10 minutes to allow the chloroform to fully separate.
  • Drain the lower layer (chloroform) carefully into a separate, clean beaker. Leave behind the aqueous layer containing by-products such as sodium acetate and excess bleach.

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Step 6: Purification and Washing of Chloroform

• Procedure:
  • Wash the separated chloroform with 10 mL of distilled water in a separation funnel. Shake gently and allow it to settle. Repeat this process three times to remove impurities and any residual aqueous layer.
  • Optionally, add 5g of anhydrous calcium chloride (CaCl₂) to the chloroform to remove any traces of water. Let it sit for 30 minutes, then filter through a Büchner funnel to remove the drying agent.

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Haloform Reaction Details:

• The haloform reaction involves the breakdown of acetone (or methyl ketones) when reacted with a halogen source like sodium hypochlorite in the presence of a base.
• In this case, acetone reacts with sodium hypochlorite and sodium hydroxide to yield chloroform (CHCl₃) and sodium acetate.
• The reaction mechanism involves the deprotonation of acetone, formation of an enolate ion, halogenation at the alpha-carbon, and then cleavage of the carbon-carbon bond, releasing chloroform.

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Step 7: Yield Calculation

• Practical Yield:
  • Based on the stoichiometry of the reaction, 10 mL of acetone can produce approximately 12.3 mL of chloroform assuming 100% yield.
  • With a typical reaction efficiency of 80%, the practical yield of chloroform would be around 9.8 mL.

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Step 8: Safety Considerations and Waste Disposal

• Safety:
  • The reaction is exothermic, so it's critical to maintain temperature control using an ice bath.
  • Chloroform is toxic and should be handled in a well-ventilated area or under a fume hood. Proper personal protective equipment (PPE) such as gloves and safety goggles must be worn.
• Waste Disposal:
  • The aqueous by-products, including sodium acetate, should be neutralized before disposal.
  • Any residual chloroform must be stored safely in a properly labeled container and disposed of according to local hazardous waste regulations.

 

[Osmosis Vanderwaal]

I do this about twice a month. Some tips for the home chemist.
1.yes its regular bleach, which is often 5% hypoclorite, but maximum strength bleach and pool chlorinated are 7.5 and 10% respectively, don't use splashless bleach.
2. Put them in the fridge overnight or even the freezer, slushy is a great place to start. When you open them,you need to take at least 30ml out,then add the acetone our it in and don't shake it. After a half hour shake it. We are slowing down the reaction by not shaking it at first, we ain't trying to get it get hot. At 2 hours shake again and you can tighten the caps. Put them back in the fridge. Check them in a few hours (6-10) and let any gas off
3. Wait 24 hours. For the reaction to complete.mitmdoesnt complete in 12 hours for sure and there's maybe a time earlier than 24 that it might be Don, but it depends on the temperature.
4. If you let it get hot, it's going to make yellow chloroform. If you do this all room tep you'll get yellow chloroform.
5. Dump most of the salt water out of the containers, it should be clear and it should smell like chlorine ( the water) when you get down to the last couple of cups, pour it out into a container so if any choroform slips by you catch it. I'm thinking I get about 75ml per gallon of bleach/60 ml acetone. The ratio is 3:1. It takes 3 hypochlorite molecules to chloronate 1 acetone, so by moles 3:1. IMPORTANT NOTE when you calculate the moles, subtract a little acetone because if there is any acetone left the end, it's got an unfixable problem because acetone misces with both chloroform and water so your chloroform will not dry.
6 after I've collected all of the crude in the seperatory funnel, and separated the water. I put the chloroform in the back of the freezer for 2 days and the water, since it won't mix with chloroform, stays together in puddles and bubbles and freezes out quite well. I get at least 10ml of water out of chloroform that was separated in the funnel (100ml) now you won't ND nearly as much drying agent just takenit out of the freezer and dump the chloroform out. The ice has mostly stayed in the jars because it made a ring all the way around the inside that holds it in the beaker, cup, whatever. You might want to distill it to get that that sodium acetate off of there,which has 1 use as far as I know and it's a neat trick. I'm sure there are other uses, but you don't need it in your chloroform.
Chloroform has an intriguing smell that makes you want to keep smelling it. It's not chlorine smell it's dry and sort of minty or menthol smelling.