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MEDICAL CHEMISTRY > LECTURE 8 (Polyfunctional compounds) > Flashcards

LECTURE 8 (Polyfunctional compounds) Flashcards

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1
Q

What are Amines and what are their properties?

A

Amines contain one or more organic groups bonded to nitrogen in compounds with the general formulas RNH2, R2NH and R3N

PROPERTIES
- Organic derivatives of water
- Classified as primary, secondary or tertiary (according to how many organic groups are individually bonded directly to the nitrogen atom)
- Each amine nitrogen atom has a LONE PAIR OF ELECTRONS -> responsible for chemistry of amines -> fourth group bonds through lone pair, QUATERNARY AMMONIUM ION formed -> permanent +ve charge and forms ionic compounds with anions

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2
Q

What are the properties of the groups bonded to the amine nitrogen atom?

A
  • May be alkyl or aryl groups
  • May or may not contain other functional groups
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3
Q

What is NH2?

A

An amino group

[Aromatic amines are an exception to this rule -> Simplest aromatic amine is called “aniline” and derivates are called anilines]

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4
Q

What does the lone electron pair on the nitrogen amines cause?

A

It causes amines to act as either WEAK BRONSTED-LOWRY BASES/LEWIS BASES by forming a bond with an H+ ion from an acid or water

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5
Q

What are the boiling point properties of Amines?

A
  • Engage in hydrogen bonding -> primary + secondary amines have higher boiling points than alkanes of similar size
  • Lower boiling points than alcohols of similar size
  • Tertiary amines have lower boiling points than secondary and primary amines -> Tertiary amines can’t hydrogen bond
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6
Q

What are the properties of Amines?

A
  • Simplest amines are gases, others are liquids
  • Volatile amines have unpleasant odours
  • Simple amines are water-soluble because of hydrogen bonding with water
  • Amines are weak Bronsted-Lowry/Lewis bases
  • Many are physiologically active + toxic
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7
Q

What are Heterocycles?

A

Compounds that contain atoms other than carbon in the ring

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8
Q

Describe the reversible reaction between neutral amines and ammonium ions

A
  • Reversible
  • Ammonium ions can react as acids in the presence of bases to regenerate amines
  • Equilibrium exists in solution with pH as high as 8
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9
Q

What are Ammonium salts?

A

Composed of a cation and an anion and are generally odourless, white, crystalline solids that are much more water-soluble than neutral amines since they are ionic

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10
Q

What are Alkaloids?

A

Roots, leaves and fruits of flowering plants that are a rich source of nitrogen compounds

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11
Q

What is the difference between an Aldehyde and a Ketone?

A

Aldehyde = carbonyl group is bonded to at least one hydrogen atom so that the -CHO group falls at one end of a molecule

Ketone = carbonyl group is bonded to 2 carbon atoms and is never at the end of the molecule

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12
Q

Describe a carbonyl group

A

A carbonyl group has a carbon atom and an oxygen atom connected by a double bond

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13
Q

What are the bond angles found between the three substituents on the carbonyl carbon?

A

120 degrees

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14
Q

Are aldehydes and ketones soluble in organic solvents?

A

YES

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15
Q

Are aldehydes and ketones soluble in water?

A

YES - the ones fewer than 5/6 carbons

Explanation: they are able to hydrogen-bond with water molecules but with increasing numbers of carbon atoms, aldehydes and ketones become more alkane-like and less water-soluble

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16
Q

What are the properties of Aldehydes and Ketones?

A
  • Polar due to presence of carbonyl group
  • Cannot hydrogen-bond with one another -> lower boiling points than alcohols but higher boiling points than alkanes due to polarity
  • Typically liquids
  • Simple aldehydes and ketones are water-soluble due to hydrogen bonding with water molecules + ketones are good solvents
  • Distinctive odours
17
Q

Simple ketones are less toxic than simple aldehydes (TRUE/FALSE)

A

TRUE

18
Q

What do you get if you oxidise an Aldehyde and a Ketone?

A

Aldehyde -> Carboxylic acid
Ketone -> No reaction

[since ketones cannot be oxidised, mild oxidising agents are used to distinguish between the two -> TOLLENS’ REAGENT/BENEDICT’S REAGENT]

19
Q

Describe the reduction of carbonyl groups

A

Reduction of carbonyl group occurs with the addition of hydrogen across the double bond to produce an -OH group

Aldehydes -> reduced to primary alcohols
Ketones -> reduced to secondary alcohols

20
Q

What are Carboxylic acids?

A

Carboxylic acids have an -OH group bonded to the carbonyl carbon atom

21
Q

What are the derivatives of Carboxylic acids?

A
  • Esters
    [have an -OR group bonded to the carbonyl carbon atom]
  • Amides
    [have an -NH2, -NHR or -NR2 group bonded to the carbonyl carbon atom]
  • Acid anhydrides
    [formed when two carboxylic acids join together by eliminating a molecule of water]
22
Q

Carboxylic acids and their derivatives commonly undergo which reactions?

A

Carbonyl-group substitution reactions

[A group replaces the group bonded to the carbonyl carbon atom]

23
Q

What are the properties of Carboxylic acids?

A
  • Behave as weak acids -> surrender hydrogen of COOH to bases and establish acid-base equilibria
  • Form hydrogen bonds with each other -> liquid at room temp
24
Q

What is an Acetyl group?

A

Acetoic acid losing its “OH” group

25
Q

Why do Esters have a lower boiling point than carboxylic acids from which they were derived?

A

When the -OH of the carboxyl group is converted to the -OR of an ester group the ability of the molecules to hydrogen-bond with each other is lost -> simple esters have a lower boiling point than the acids from which they were derived

26
Q

Do Amides have a higher or lower boiling point than the acids from which they were derived?

A

Higher

Explanation: Unsaturated amides can form multiple hydrogen bonds to other amide molecules -> higher boiling point than acids from which they were derived

27
Q

What are the properties of Low-molecular-weight unsubstituted amides?

A
  • Solids
  • Soluble in both water and organic solvents
28
Q

What is the difference between Monosubstituted amides and Disubstituted amides?

A

Monosubstituted amides = can form hydrogen bonds to each other

Disubstituted amides = cannot hydrogen bond -> lower boiling point

29
Q

What is the difference between an Amine and an Amide?

A

The nitrogen atom is bonded to a carbonyl-group carbon in an amide but not in an amine

Explanation: The +ve end of the carbonyl group attracts the unshared pair of electrons on nitrogen strongly enough to prevent it from acting as a base by accepting a hydrogen atom -> Amides are not basic like amines

30
Q

What are the properties of Carboxylic acids, Esters and Amides?

A
  • All undergo carbonyl-group substitution reactions
  • Esters + Amides are made from carboxylic acids and can be converted back
  • Carboxylic acids and unsubstituted/monosubstituted amides exhibit strong HYDROGEN BONDING to one another; disubstituted amides and esters do not hydrogen bond to one another
  • Simple acids and esters are liquids; all unsubstituted amides are solids
  • Carboxylic acids give acidic aqueous solutions; Esters + amides are pH neutral
  • Small esters and amides are WATER SOLUBLE
  • Volatile acids have strong, sharp odors; volatile esters have pleasant, fruity odours. Amides have no associated odours.
31
Q

What is Esterification?

A

Warming a carboxylic acid with an alcohol in the presence of a strong-acid catalyst forming an ester

[Acid-catalysed hydrolysis is a reverse of esterification]

32
Q

How are unsubstituted and substituted amides formed?

A

Unsubstituted amides = formed by the reaction of carboxylic acids with ammonia

Substituted amides = produced in reactions between primary and secondary amines and carboxylic acids

33
Q

Describe ester hydrolysis in the presence of a strong acid catalyst

A

An ester treated with water in the presence of a strong acid catalyst forms a CARBOXYLIC ACID and an ALCOHOL

[water pushes equilibrium to the right -> more products]

34
Q

Describe ester hydrolysis in the presence of a base

A

Called “saponification” forms a CARBOXYLATE ANION and an ALCOHOL

35
Q

Are amides extremely stable in water?

A

YES

Explanation: Yes but undergo hydrolysis with heating in the presence of acids or bases -> products are carboxylic acid and amine from which the amide was synthesised

MEDICAL CHEMISTRY (10 decks)

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