LABORATORY TOPICS Flashcards
Define an Enantiomer.
non superimposable mirror images. have opposite configurations (R)/(S) at all stereo centres.
What is “achiral” ?
means there is an internal mirror plane of symmetry. Meso compounds are achiral. (superimposable on their mirror image).
Define a Diastereomer.
different configurations at some, but not all, the chiral centres.
E/Z refer to priority groups and trans/cis refer to longest chain. [true or false]
TRUE.
What is distillation? What is it used for?
Separation process, used to purify liquids. transfers vapour to a different apparatus and condenses.
Difference between fractional and simple distillation.
fractional is used for liquids with similar boiling points. simple is used for liquids with different boiling points.
What does the temperature change represent on a Liquid-Vapour Diagram?
Once you’ve finished distilling the first liquid at TempA, the temp will change to begin boiling the more volatile liquid.
Why use a Reflux apparatus?
allows a reaction to take place at a HIGH constant temperature (boiling point of the solvent) without loose due to evaporation.
In TLC analysis, how can you compare polarity?
If the plate is silica (polar), the less polar compounds will move further up the plate as there’s less “interactions” with the plate. Rf value is another way. Lower Rf values means more polar molecule.
How can you move the dots further up the plate?
Make the solvent more polar.
Name 3 main Reductive Processes.
- Catalytic Hydrogenation (adding H2)
- Hydride Reduction (adding hydride, then H)
- Dissolving Metal Reduction (adding e- then p+)
What acts as the Nucleophile in Hydride Reduction?
the hydride H- (sourced from reagents LiAlH4 or NaBH4) and reduces the carbonyl.
What functional groups can NaBH4 reduce?
can not reduce carboxylic acids, esters or ethers. Only ketones and aldehydes.
Describe the effect of the Grignard Reagent.
The magnesium creates a partially bonded carbanion. This makes the R group of R–MgX act as a good nucleophile. The reagent adds to the electrophilic carbonyl group !!
The grignard reagent acts as an electrophile and is basic. [true or false]
False. The reagent is NUceleophilic and Basic.
In aldol addition, what is the nucleophile and what is the electrophile?
Enolates act as a good Nu and Carbonyl C acts as electrophile.
Explain briefly the aldol addition.
An enole/enolate from an aldehyde/ketone reacts with another aldehyde/ketone forming a new C-C bond. After this, they often go through dehydration.
What is required for the aldol addition to occur?
there must be an alpha-hydrogen in the structure. (i.e., adjacent to the C=O). as well as a base catalyst to deprotonate said hydrogen.
Which are more reactive to Nucleophiles, aldehydes or ketone?
aldehydes. consider resonance and hyper conjugation.
Explain a conjugated alkene.
2 double bounds connected by a single bond, share delocalized electrons, overlapping p-orbitals. trans orientation is more table than cis.
When dehydrating alcohol’s, what product is most favoured? (consider diene product)
The conjugated formation is the most favoured product, in Diels-Alder reaction
explain Schiff’s Reagent
to test for aldehydes. positive when magenta colour appears.
explain Tollen’s Test
to test for aldehydes. positive when silver/metallic colour appears. redox reaction occurs.
explain Iodoform Test
to test for methyl ketones. positive when pale yellow solid crystals form.
