lab Flashcards
Sodium Hydroxide _______________
- corrosive- causes burns
Gramine is _________________
Harmful -if swallowed or in contact with skin
Indole is ____________-#
4
3 Harmful- in contact with skin and if swallowed. Irritant. May cause serious eye damage
Indole is ____________
Harmful- in contact with skin and if swallowed. Irritant. May cause serious eye damage
AQATIC LIFE
Dimethylamine is __________________
4
Highly flammable. Harmful by inhalation and if swallowed.
Corrosive causes burns
Petroleum ether is _____________
5
Highly flammable. Harmful. May cause lung damage if swallowed. Do not breathe gas. Avoid skin contact, DROWSY
Acetone is _____________
3
Highly flammable- irritating to eyes, DROWSINESS
Formaldehyde is ___________
7
Toxic by Inhalation, Skin contact and if swallowed Dangers of irreversible effects Corrosive Carcinogenic category 3 Caused burns Sensitization by skin contact
how did the recrystallization happen
Boiling mixture used for recrystalization
Pet ether 40ml
Then add 5ml acetone
describe the principle of recrystallization
Principle of crystallisation
To purify the product by reforming the crystal with impurities remaining in solution
Why use a Boiling stick?
So solvent will boil evenly and will not boil over
Gramine is very soluble in acetone
Slower cooling produces _________________
better quality crystals formed
What chemicals in the synthesis of Gramine require students to wear gloves AND handle in the fume cupboard.
- Indole
- Dimethylamine
- Formaldehyde
- Acetic acid
What chemicals in the synthesis of Gramine require students to JUST wear gloves
- NaOH
- Petroleum ether
- Acetone
- Gramine
Why does the dimethylamine, formaldehyde, and glacial acetic acid need to be ice-cooled?
The iminium ion only forms when it is cold
What happens to the formulations when dimethylamine, formaldehyde, glacial acetic acid and indole is heated?
A clear solution forms with a rise in temperature
What temperature water bath is used to warm the dimethylamine, formaldehyde, glacial acetic acid and indole mix is heated?
35oC for 30 mins
What is added to dimethylamine, formaldehyde, glacial acetic acid and indole mix after it is heated in a water bath?
Dilute sodium hydroxide solution OR NaOH
How can the first lots of crystals form after adding NaOH?
Cooled down (ice bath) and the white precipitate forms
How are the crystals separated from suspension?
Vacuum filtration after cooling in an ice bath
What can be used to wash the crystals in vacuum filtration for the first time?
Cold water - wash twice
How can the first crystals be treated to remove as much water as possible from the suspension?
- Vacuum filtration
- Oven at 60oC
What should be done after the first crystals have been dried, in order to purify them?
Recrystallisation
What agents are used to recrystallise the gramine?
- Acetone
- Petroleum ether
In what way are the acetone and petroleum ether added to the crystals in the recrystallisation step?
Start with a boiling mixture of 40 mL petroleum ether and 5 mL acetone, then increase gradually the acetone content with 5 mL additions, until all the gramine has just dissolved in hot solvent.
How should dimethylamine, formaldehyde and acetic acid be pipetted?
Use separate, graduated, glass pipettes from ‘stock bottles’ and do not rinse the pipettes with water or for reuse. Use the correct pipette:
1mL - Acetic acid
2mL - Formaldehyde
5mL - Dimethylamine
How can the mass of the non-recrystallised and recrystallised powders be calculated?
Find the mass of a watch glass first, then transfer the solid to it, dry it in the oven (to constant mass or until freely flowing) and then obtain the mass
Will the (gramine) crystals dissolve in pet ether?
The solid will not dissolve as it is not soluble
What amount of acetone is expected to be used to make it soluble?
~15mL
Why should the process allow for slow crystallisation?
Slower cooling produces better quality crystals - and more solid forms
The expected mass of product does not look as if it has formed after the acetone AND pet ether has been added - why might this be?
Too much acetone may have been added
The expected mass of product does not look as if it has formed after the acetone AND pet ether has been added - what can be done to recify this?
Take the flask back to hot plate and boil off half the volume of solvent. Cool in air and in an ice-bath again. More solid should form
What can be used to wash a second lot of crystals during vacuum filtration?
Pet ether (<15mL)
Why can water NOT be used to wash the second lot of crystals during vacuum filtration after recrystallisation?
Leads to poor quality crystals
Why can acetone NOT be used to wash the second lot of crystals during vacuum filtration after recrystallisation?
They will dissolve
What is donated from acetic acid that is attacked by the lone pair on formaldehyde?
H+
What nucleophile attacks the carbon on the protonated formaldehyde?
N: on dimethylamine
What ion is formed from the mechanism between formaldehyde and dimethylamine?
Iminium ion
What synthesized ion is attacked by indole in the synthesis of gramine?
Iminium ion
What other agent is necessary for the formation of Gramine?
- Dimethylamine
- Formaldehyde
- Acetic acid
- NaOH
What other agent is necessary for the formation of Gramine?
- Formaldehyde
- Acetic acid
- NaOH
Dimethylamine
Formaldehyde
- Acetic acid
What is the end structure of Gramine?
draw it
