Chem P2 Flashcards
When synthesising an organic liquid, what main drying agent is used?
Anhydrous calcium chloride
CaCl2
When an alkene and alcohol group are present, how do you write it? E.g. 6 Carbons (OH on C1, C=C on C3)
Hex-3-en-1-ol
Steps of purifying an organic LIQUID
- Pour mixture into separating funnel
- Invert to mix contents
- Remove the aqueous layer (either density given or add some water and see which layer increase in vol)
- If preparation involves acid- remove acid impurities by adding NaHCO3. Holding funnel upside down, release gas by opening stopper and then remove aqueous layer)
- Dry liquid by adding drying agent (anhydrous calcium chloride) add into some powder remains (may need to leave in between additions.
- REDISTIL at boiling point of desired product.
What does reflux apparatus look like?
What does distillation apparatus look like?
How is a pi bond formed? Diagram
Description of how a pi bond is formed
- A carbon uses 3 of it’s 4 electrons to form sigma bonds
- The 4th electron from each C occupies a p orbital which overlaps SIDEWAYS with another p orbital
- This leads to formation of a pi bond
Steps of purifying an organic SOLID
- Filtration under reduced pressure
- Recrystallisation
- Melting point determination
Description of Filtering under reduced pressure
- Attach rubber tubing to buchner flask, with other end of tubing on filter pump or vaccuum, then fit Buchner funnel onto flask.
- Switch on the vaccuum pump or tap
- Place filter paper into funnel, then wet with whatever solvent has been used.
- Slowly pour reaction mixture into funnel, remembering to rinse out the beaker with the solvent used.
- Rinse the crystals formed with more solvent and leave under suction to dry.
Description of recrystallisation
- Warm chosen solvent either in a water bath (if flammable) or with a bunsen burner.
- Tip impure sample into a beaker
- Slowly add the minimum amount of hot solvent needed to dissolve the solid
- Once the solid has dissolved, allow solution to cool and crystals will form.
- Filter crystals under reduced pressure
- Add ice cold solvent to crystals and allow them to dry on filter paper
What can we achieve via melting point determination?
We can see if the organic solid is pure or not.
If product is pure, it will have a very sharp melting point of 1-2 degrees.
If it contains impurities, it will melt over a wide range of temperatures
Impure sample has a lower MP than a pure sample
Different methods of determining melting point
- Using electrically heated melting point apparatus
- Using an oil bath or thiele tube method.
What is an alicylic compound?
An aliphatic compound arrange in non-aromatic rings with or without side chains
What are the Cahn- Ingold- Prelog rules?
Rules of E/Z isomerism:
* If the highest priority groups are on the same side as each other: Z
* If the highest priority groups are on opposite sides:
* Higher the atomic number of groups directly attached to C atom in C=C –> Higher priority
Why does e.g. heptane have a higher B.P. than Hexane
Heptane has a longer chain, greater surface area for contact and therefore stronger london forces, which require more energy to overcome
