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PL2002 > Lab Questions > Flashcards

Lab Questions Flashcards

1
Q

How is the Rf value calculated?

A

Rf = distance of spot/distance of solvent

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2
Q

Which compounds travel further on TLC plates?

A

Non-polar substances

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3
Q

If TLC liquid is more polar, do polar substances travel more or less distance?

A

More distance

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4
Q

What is the equation to find the concentration?

A

n = m/GFM

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5
Q

What are equivalents?

A

Equivalents assess which reactant is limiting and which is in excess

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6
Q

What details are needed for a correct graph?

A

Title
Labelled axises
Units on axis
Axis takes up half of graph paper

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7
Q

How does p-aminophenol become paracetamol?

A

P-aminophenol is acylated to form paracetamol

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8
Q

How is paracetamol purified?

A

By recrystallisation

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9
Q

Why is ethanoic acid water soluble?

A

Carboxylic acid is hydrophilic

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10
Q

Why is paracetamol not very water soluble?

A

Aromatic ring is hydrophobic

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11
Q

How is para-aminophenol formed?

A

Phenol is nitrated to form ortho and para nitrophenol
P and O nitrophenol are separated
P-nitophenol is reduced to p-aminophenol (NO2 becomees NH2)

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12
Q

How is percentage yield calculated?

A

% yield = recrystallised yield/actual yield x100

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13
Q

How can impurities be checked for?

A

Low MP and larger MP range

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14
Q

Why is sulphuric acid added to powered plant?

A

To convert the free base to a salt

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15
Q

Why was DCM used?

A

As an organic solvent to remove impurities as free base is in salt form so aqueous soluble

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16
Q

Why was anhydrous sodium sulphate used?

A

As a drying agent

17
Q

Why is the vitali-morin’s test done?

A

To test for the presence of tropane alkaloids

18
Q

What colour is the Vitali-morin’s test?

A

Purple

19
Q

Why was TLC done for the alkaloids?

A

To examine the the resulting alkaloids for the presence of atropine and hyoscine

20
Q

What can be concluded about hyoscine?

A

Hyoscine is very non-polar as it travelled very far up the plate

21
Q

Why was methanol added to the dried solid?

A

As an organic solvent to extract the free base

22
Q

Why are barbiturates acid?

A

They can donate a proton

23
Q

How is the barbiturate molecule stabilised?

A

Electrons are delocalised around the ring to stabilise the molecule

24
Q

Why was analysis done at different pHs?

A

To mimic different body parts

25
Q

When are barbiturates ionised?

A

In basic solutions

26
Q

How do barbital and phenobarbital differ?

A

Phenobarbital has an aromatic ring so is more lipophilic, has higher logP and is less water soluble than barbital

27
Q

Why was the first solution scanned at multiple dilutions?

A

To construct an absorbance vs concentration calibration curve
Used to determine concentration later in the experminent

28
Q

Why was the spectrometer blanked?

A

To give λ max to analyse further dilutions

29
Q

What happens to the concentration in aqueous as pH increases?

A

Drug aqueous concentration increases as pH increases

30
Q

What happens to %ionisation as pH increases?

A

As pH increases, % ionisation increases as barbiturates are ionised in basic solutions

31
Q

What does SMILES stand for?

A

simplified molecular-input line-entry system

32
Q

Why molecular weight under 500?

A

Follows Lipinski’s rule of 5

33
Q

Why is logP not the best measure of lipophilicity of drugs?

A

logP can only be used for unionised molecules and most drugs are ionised at physiological pH

34
Q

What is the percentage ionisation of a drug when pKa=physiological pH?

A

50%

35
Q

What is the percentage ionisation of an acidic drug when pH = pKa + 2?

A

99%

36
Q

What is the percentage ionisation of a basic drug when pH = pKa - 1?

A

90%

37
Q

Why was concentrated ammonia added?

A

To convert the salt to a free base

PL2002 (7 decks)

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