CHEM 235 Exam Prep – Organic Chemistry Lab Techniques

Here are the Flashcards I made – Glossary of terms https://quizlet.com/148816707/chem-235-glossary-flash-cards/

Laboratory maintenance

  • Do not put chemical back into original containers
  • Measure out hazardous chemicals at the fumehoods and transport them in closed containers
  • Clean your glassware with soap & multiple rinses with water at the end of each lab so it’s clean for the next lab ( video on proper cleaning)

https://groups.chem.ubc.ca/safetytraining/DZEorganiclabCD1/index.html

Intro Video 1- Personal Protective Equipment

  • No sandals or open toed shoes. Wear leather closed toes shoes
  • Cover legs. no shorts
  • wear long sleeved shirt to cover your arms
  • wear knee length lab coat
  • do not wear hat
  • tie up your long hair. you might have to tuck your hair under the collar
  • wear protective safety goggles or normal prescription eyeglasses that are at 4 cm wide and tall. Wear glasses at all times while in the lab

Intro video 2 – Cleaning glassware

  • the successful outcome of experiments can be affected by how clean the glassware are.
  • sponges for cleaning the benchtops
  • begin cleaning by eliminating as much solid waste as you can. choose the appropriate size brush to clean. Add small amount of detergent and hot tap water and then scrub with brush. rinse with tap water thoroughly. If still dirty, use Comet.
  • be very careful when cleaning the inner tube of the condenser. It is not necessary to clean the outer jacket or outlets
  • do not put a brush into the tip of a separatory funnel
  • shake out water after rinsing
  • put the glassware in your locker on its bottom. the opening must be exposed to air
  •  do not use paper towel to dry
  • In some cases, use acetone at the acetone washing station
  • If you need to dry quickly to use again, use acetone. If it will be in contact with water based solution, acetone is not necessary.

Introductory video 3- waste disposal

  • there’s a solid waste container in a large fumehood. don’t put glass there.
  • glassware such as capillary tubes should go to the glass waste container.
  • flush water based solutions down the sink e.g. the hcl, h2so4, naoh, nahco3 (inorganic acids and bases). flush with running water for at least a minute
  • put organic solvents into the red cans labelled liquid organic waste e.g. diethyl ether, methylene chloride. the container is next to the solid waste.
  • acetone has its own special disposal can beside the glass waste.

What to do in case of a fire

  • turn off the heat source
  • place a watchglass over the top of the vessel
  • try to remove solvent bottles and equipment away from fire
  • fires involving small amounts of solvent will burn out harmlessly
  • dry chemical or co2 fire extinguisher for bigger fires

What to do for spills

  • flush, safety shower
  • get rid of clothes with chemical spills
  • sweep off floor, wipe up with wet sponge if inorganic. if organic, use paper towel
  • eye- flush with water for 15- 30 minutes

WHMIS

  • class a = compressed gas
  • class b = flammable and combustible material
  • class c = oxidizing material
  • CLASS D 1 =  poisonous and infectious
  • class d = materials causing other toxic effects
  • class d3 = biohazardous
  • class e= corrosive
  • class f= dangerously reactive material

evaluation

  • do prep work
  • do homework questions due at the start of lab
  • the quality of your product matters
  • there will be quizzes
  • **remember that you must always use ink

 

Extraction

  • water Based solution
  • Immiscible organic solvent e.g. ether
  • Separatory funnel
  • Dissolve compounds in the ether solution
  • Split the aqueous solution into 3. Use a graduated cylinder
  • Funnel never more than 2/3 full
  • Fix and invert and release pressure
  • No whoosh sound is good
  • A bit that is mix, do its own beaker
  • Pour out the top of funnel and cork it up
Recrystallization
  • Cork and ground glass joint
  • Boiling chip
  • Container with water
  •  Put in the flash, add boiling chip
  • Add just enough solvent to cover the compound
  • Wes condenser to the outlets, wet the ends of the tubing first
  • Put the whole apparatus.
  • Two sided clamp LOOSELY around body of wes condenser
  • Put the tubing over the metal thing to keep it out of the way.
  • Attach the lower out to the water source and let the other one spill out into the sink. Be gentle when you turn it on.
  • Boil at high heat
  • Use a paper, folded, thick strip around the top of the flash to stir the flask
  • If not dissolve when boil, dropper some solvent until dissolves
  • Remove flash from hot plate USING A CLAMP around the flash.
  • Remove from the wes condenser and clamp at an angle to the bench. Do not disturb in any way.
  • Evaporate away solvent, add incompatible solvent ( compound does not dissolve in this solvent), ice water bath
Simple distillation
  • 100 ml Rb
  • Still head adaptor
  • thermometer
  • Collection vessel

Filtering Unwanted solids

  • Gravity filtration using filter paper
  • Erlenmeyer flask large enough that solvent occurs no more than 1/2 its volume
  • Glass filter funnel
  • You want to keep the solvent but not the solids
  • Use the small ring clap with a gap
  • Hot filtration – preheat in oven
  • Pour solution down a rod to avoid splash
  • Rinse flash with ice cold solvent to get rid of bits
  • If flow slows, push the filter paper down
  • KEEP the SOLVENT
Filtering wanted solids – suction filtration
  • Suction trap = the big one
  • Use three pronged clamp for the filter flash
  • Temporarily disconnect the vacuum before you add the crystals so you don’t break your crystals
  • Press down on funnel for better seal
  • Use ice cold solvent or use the MOTHER LIQUOR, pour down the stirring rod
  • Do suction for several minutes to dry the crystals
  • Use spatula to flip onto a watch glass and let it dry
  • Cover with weighing paper to protect
  • It’s easier to take crystals off the filter paper when dry
Preparing a sample for melting points
  • Micro cover glasses
  • Capillary tubes
  • Drop tube
  • Fischer Johns or mel temp
  • Grind the solid into fine particle -> crush on watch glass using a test tube
  • Fischer john -> all crystals touching it each, none too close to edge, use copper cooled in ice bath to cool
  • 3 -4 mm in capillary tube, drop tube more than once, firmly packed no more than 2-3 mm
Taking melting points
  • Heating block/sample well
  • If known, raise temp to max until 15-20 below expected melting point. Reduce the rate so rate rises 2 degrees per minute.
  • First drop of liquid amongst the crystals. 2nd temp – whole solid mass turns to liquid. The melting point is both of these numbers
  • If unknown, max until melting is noticed. The observed temp is lower than the true melting point because lag between thermometer reading and actual temperature of heating block. Allow cooling until 20 degrees lower than observed melting point
  • Plastic beaker with ice -> wipe off moisture. Use hot hands device.
  • All used in glass waste container
  • Calibration equation – CORRECT THE TEMP READING USING CALIBRATION EQUATION. Y = true mp. x.= observed mp
  • Use hair dryer to cool. If known, heat until 10 degrees below known mp. Preliminary reading will be lower than true. Let cool until 20 degrees lower than preliminary reading. Heat at 2 deg increase per minute.
Calibrating a thermometer
  • Ice bath in 400 ml beaker glass.
  • Immersion line is covered by water. Stir ice bath gently to ensure even distribution of temperature. If not exactly 0, adjust your readings. For distillations, glycerol at tip, insert into stilled adaptor until immersion line is completely covered.
Thin layer chromatography-
  • Rapid separation and qualitative analysis of small amount of material
  • Cannot be used for volatile compounds
  • Partition of compounds between moving liquid phase and solid stationary phase
  • 100 ml beaker
  • 1/2 moon paper
  • Silica gel plate
  • Pencil and ruler
  • Spotting solvent
  • Dissolve your compound in a volatile solvent, spot onto your plate, the volatile solvent evaporates and the compound gets absorbed onto solid plate.
  • Dip plate into developing solvent, capillary action
  • Compound attracted to moving liquid phase (the developing solvent that moves by capillary action) and moves with it. Different substances attracted to moving phase differently so moves different amounts.
  • ** LEAST POLAR SUBSTANCE MOVES FURTHER since liquid phase is less polar than the solid phase. **
  • Rf = distance traveled by compound/ distance traveled by the solvent from t
What to do if there’s a fire
  • Turn off the heat
  • Put a watch glass on top to smother the flames
  • Remove solvents and equipment from area
  • Most fires will burn out by themselves but if not, use fire extinguisher

 

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