Functional groups with acidic behaviour Flashcards

1
Q

What are ionic bonds?

A

occurs due to the electrostatic interaction between two charged species (cation and anion)

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2
Q

What are acidic functional groups and their properties (5)

A
  1. species (groups) that can donate protons
  2. Strong acids have an equilibrium that lies to the right (products) and has large Ka and small pKa.
  3. Weak acids have an equilibrium that lies to the left (reactants) and have small Ka and large pKa.
  4. Ka = [A-][H+]/[HA]
  5. pKa = -logKa
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3
Q

What are carboxylic acids and their properties (7)

A
  1. consists of a carbonyl group and a hydroxyl group (COOH), as a consequence, it promotes strong intermolecular interactions
  2. R can be aromatic or aliphatic.
  3. =O and O act as H bond acceptors
  4. H acts as an H bond donor.
  5. The group is planar, containing sigma and pi bonds and sp2 hybridisation.
  6. The anion carboxylate is stabilised by resonance.
  7. aliphatic carboxylic acids have pKa values of 4-5
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4
Q

What is the nature of ‘’R’’ and acidity (3)

A
  1. the value of pKa varies considerably as a function of the nature of R
  2. EWG stabilise the negative charge, therefore stabilising the carboxylate, increasing the acidity (lower pKa)
  3. EDG do not stabilise the negative charge, therefore, destabilises the carboxylate, decreasing the acidity (higher pKa)
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5
Q

What are phenols and their properties (6)

A
  1. Phenols consist of a benzene ring bonded to an OH group.
  2. O acts as an H bond acceptor and H as an H bond donor.
  3. Phenols are more acidic than alcohols because the negative is stabilised by resonance (delocalised on the aromatic ring)
  4. EWG increase the acidity of the phenol because it favours the delocalisation of the charge on the ring
  5. EDG decrease the acidity of the phenol because it disfavours the delocalisation of the charge on the ring
  6. CYP450-mediated oxidation of phenol leads to the formation of 1,2 and 1,4-dihydroxybenzene, which are easily oxidised to ortho-quinone and para-quinone (redox toxicity). The hydroxylation of the ring occurs via an epoxide intermediate (toxic electrophile)
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6
Q

What are the properties of sulfonamides (2)

A
  1. R can be aliphatic or aromatic.
  2. The proton on the sulphonamide group is acidic because of the EWG effect of the sulphonic group and because the anion resulting from the deprotonation is stabilised by resonance.
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7
Q

What are the properties of sulfonylureas (2)

A
  1. R and R1 can be aliphatic or aromatic
  2. have a similar stabilisation as the one for sulfonamides (acidic because of the EWG effect of the sulfonic group and because the anion resulting from the deprotonation is stabilised by resonance)
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8
Q

What are the properties of sulfates and phosphates (4)

A
  1. Sulfonic acids are very strong acids, which deprotonate in aqueous environment
  2. pKa = 0-2
  3. The anion is stabilised by resonance: the charge is delocalised on the sulfonic group
  4. similarly, phosphonic acids are very strong acids (pKa1 = 1.5, pKa2 = 6.5)
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