Chapter 28 Nitriles And Organic Synerheis And Pracrical Work Flashcards
What is a nitrile
Anything with nitrile group CN, where triple bond
How are nitriles made
2 ways
What both reactions and what do they need
What does secon one forme
1) reacting haloalkanes with KCN in an nucleophikic substitution reaction
2) we know they can be reduction reactions of HCN , using H2so4 and NACN instead (more safe), of aldehydes and ketones to firm HYDROXYNITRILES
What 2 reactions do nitriles take part in
1) Reduction of nitrile to form an amine
2) hydrolysis to form a carobykic acid and an ammonium salt
1) reduction of nitrile to form amine (easy)
Simply add 3 H2 and use Ni catalyst at 423K, addition reaction essentially and gives amine
2) hydrolysis of nitrile to form carbox IMPORTSNT
Use 2 H2O and Hcl and heat
Will give cabroylic acid and ammonium chloride salt
What is filtration under reduced pressure used for ?
When trying to filter a solid produce like crystals from a solvent or liquids = a better option than just filter paper
What equipment and how do you do it
- Buckner flask connected to Buckner funnel and filter paper
- connected to a tap or vacuum pump
1) connect one end of tubing ti vacuum outlet for filter pump and other to Buckner flask
2) fir the butcher. Funnel to the Buckner flask ensuring it’s a tight fit using a bung
3) switch in the pump and check for good suction by turning tap on and feeling
5) now add filter paper inside and wet this using thr solvent , should see it go down max sucked
5) now slowly pour thing inn , rinse beaker so all solute gone in
8) now let dry to form crystals
Recrystallisation used for what?
Solid product after filtering will contain impurities, so you want these to cut
- impurities could be leftover solvent , could be something random, some of the reactant etc
How to recrystallise
- need to try use minimum amount of hot solvent to dissolve your solutes
Whatever your hot solvent is if lsmmable use water bath to heat if not fan heat
1) heat it up in a flask and warm solvent
2) now slowly add the solvent solowly whilst stitokg impure sample until it dissolves
You want the MINIMUM AMOUNT IF HOT SOLVENT TO DISSOLCE IT , and stop then
3) once done, allow to cool and crystals will begin to form again
4) when no more form, simply filter again under reduced pressure it get pure cut slabs nowm
Melting point determination
Melt a capillary tube and put some crystals in
Use the electric appraise and place into sample hole
2) add a 300° thermometer in the thermometer hole
3) start to heat it up whilst observing sample
4) once it melts, record the melting point
Like a titirstion do again but as it approaches slowly heat to get accurate melting point t
Finally what will melting point mean for purity
If melts over a sharp range if 1-2 degrees similar then pure snd sntches what melting point should be
Why is MINIMUM AMOUNT OF HOT SOLVENT USED (minimum and hot)
IMPORTANT MINIMUM
Hot to make it dissolve easier)
Minimum so it becomes SATURATED and allows the crystals to form, must be less volume so thst it’s saturated otherwise CRYSTALS WONT FORM FAST ENOUGH
