lab

Question 1

Sodium Hydroxide _______________

Answer 1

• corrosive- causes burns

Question 2

Gramine is _________________

Answer 2

Harmful -if swallowed or in contact with skin

Question 3

Indole is ____________-#

4

Answer 3

3 Harmful- in contact with skin and if swallowed. Irritant. May cause serious eye damage

Question 4

Indole is ____________

Answer 4

Harmful- in contact with skin and if swallowed. Irritant. May cause serious eye damage

AQATIC LIFE

Question 5

Dimethylamine is __________________

4

Answer 5

Highly flammable. Harmful by inhalation and if swallowed.

Corrosive causes burns

Question 6

Petroleum ether is _____________

5

Answer 6

Highly flammable. Harmful. May cause lung damage if swallowed. Do not breathe gas. Avoid skin contact, DROWSY

Question 7

Acetone is _____________

3

Answer 7

Highly flammable- irritating to eyes, DROWSINESS

Question 8

Formaldehyde is ___________

7

Answer 8

Toxic by Inhalation, Skin contact and if swallowed 
Dangers of irreversible effects
Corrosive 
Carcinogenic category 3
Caused burns
Sensitization by skin contact

Question 9

how did the recrystallization happen

Answer 9

Boiling mixture used for recrystalization
Pet ether 40ml
Then add 5ml acetone

Question 10

describe the principle of recrystallization

Answer 10

Principle of crystallisation

To purify the product by reforming the crystal with impurities remaining in solution

Question 11

Why use a Boiling stick?

Answer 11

So solvent will boil evenly and will not boil over

Gramine is very soluble in acetone

Question 12

Slower cooling produces _________________

Answer 12

better quality crystals formed

Question 13

What chemicals in the synthesis of Gramine require students to wear gloves AND handle in the fume cupboard.

Answer 13

• Indole
• Dimethylamine
• Formaldehyde
• Acetic acid

Question 14

What chemicals in the synthesis of Gramine require students to JUST wear gloves

Answer 14

• NaOH
• Petroleum ether
• Acetone
• Gramine

Question 15

Why does the dimethylamine, formaldehyde, and glacial acetic acid need to be ice-cooled?

Answer 15

The iminium ion only forms when it is cold

Question 16

What happens to the formulations when dimethylamine, formaldehyde, glacial acetic acid and indole is heated?

Answer 16

A clear solution forms with a rise in temperature

Question 17

What temperature water bath is used to warm the dimethylamine, formaldehyde, glacial acetic acid and indole mix is heated?

Answer 17

35oC for 30 mins

Question 18

What is added to dimethylamine, formaldehyde, glacial acetic acid and indole mix after it is heated in a water bath?

Answer 18

Dilute sodium hydroxide solution OR NaOH

Question 19

How can the first lots of crystals form after adding NaOH?

Answer 19

Cooled down (ice bath) and the white precipitate forms

Question 20

How are the crystals separated from suspension?

Answer 20

Vacuum filtration after cooling in an ice bath

Question 21

What can be used to wash the crystals in vacuum filtration for the first time?

Answer 21

Cold water - wash twice

Question 22

How can the first crystals be treated to remove as much water as possible from the suspension?

Answer 22

• Vacuum filtration

- Oven at 60oC

Question 23

What should be done after the first crystals have been dried, in order to purify them?

Answer 23

Recrystallisation

Question 24

What agents are used to recrystallise the gramine?

Answer 24

• Acetone

- Petroleum ether

Question 25

In what way are the acetone and petroleum ether added to the crystals in the recrystallisation step?

Answer 25

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.

Question 26

How should dimethylamine, formaldehyde and acetic acid be pipetted?

Answer 26

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

Question 27

How can the mass of the non-recrystallised and recrystallised powders be calculated?

Answer 27

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

Question 28

Will the (gramine) crystals dissolve in pet ether?

Answer 28

The solid will not dissolve as it is not soluble

Question 29

What amount of acetone is expected to be used to make it soluble?

Answer 29

~15mL

Question 30

Why should the process allow for slow crystallisation?

Answer 30

Slower cooling produces better quality crystals - and more solid forms

Question 31

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?

Answer 31

Too much acetone may have been added

Question 32

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?

Answer 32

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

Question 33

What can be used to wash a second lot of crystals during vacuum filtration?

Answer 33

Pet ether (<15mL)

Question 34

Why can water NOT be used to wash the second lot of crystals during vacuum filtration after recrystallisation?

Answer 34

Leads to poor quality crystals

Question 35

Why can acetone NOT be used to wash the second lot of crystals during vacuum filtration after recrystallisation?

Answer 35

They will dissolve

Question 36

What is donated from acetic acid that is attacked by the lone pair on formaldehyde?

Answer 36

H+

Question 37

What nucleophile attacks the carbon on the protonated formaldehyde?

Answer 37

N: on dimethylamine

Question 38

What ion is formed from the mechanism between formaldehyde and dimethylamine?

Answer 38

Iminium ion

Question 39

What synthesized ion is attacked by indole in the synthesis of gramine?

Answer 39

Iminium ion

Question 40

What other agent is necessary for the formation of Gramine? - Dimethylamine - Formaldehyde - Acetic acid

Answer 40

- NaOH

Question 41

What other agent is necessary for the formation of Gramine? - Formaldehyde - Acetic acid - NaOH

Answer 41

Dimethylamine Formaldehyde - Acetic acid

Question 42

What is the end structure of Gramine?

Answer 42

draw it