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gamsat march 2016 > Org 8 - Carboxylic Acids > Flashcards

Org 8 - Carboxylic Acids Flashcards

1
Q

What is general formula for a Carboxylic acid ?

A
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2
Q

What are Carboxylates ?

A

Salts and Anions of Carboxylic acids

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3
Q

How are Carboxylic acids named ?

A

Replace the -e of the corresponding alkane with -oic acid. The Carbonyl Carbon is the Carbon 1.

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4
Q

What is the nature of Low MR Carboxylic acids ?

A

Liquids with strong odours and high boiling points due to polarity and hydrogen bonding. They boil at much higher temperatures than corresponding alcohols.

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5
Q

Describe the solubility of Carboxylic Acids

A

Water soluble due to a good ability to hydrogen bond. > 6 Carbon chains are less water soluble but their alkali salts are quite soluble due to ionic properties.

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6
Q

Name the four important considerations for Carboxylic acids ?

A
  1. The hydrogen is weakly acidic
  2. The Carbonyl Carbon is very suscepitble to nucleophilic attack
  3. In basic conditions, the hydroxyl group is a good leaving group
    In acidic conditions, the H2O+is an excellent leaving group
  4. They can inter and intra molecularly hydrogen bond
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7
Q

Why is the hydrogen in Carboxylic acids weakly acidic ?

A

Due to its attachment to Oxygen, as the Carboxylate anion is resonance stabilised.

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8
Q

Why is the Carbonyl Carbon very susceptible to nucleophillic attack ?

A
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9
Q

What are Organic acids ?

A

This is just another name for Carboxylic acids

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10
Q

What is the increasing order of acid strength displayed by organic compounds ?

A

Alkanes < Ammonia < Alkynes < Alcohols < water < Carboxylic acids

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11
Q

What is the impact of adding electron withdrawing groups such as -Cl or NO2 to Carboxylic acids ?

A

Withdrawing groups withdraw electrons and delocalise the negative charge, which stabilises the Carboxylate anion and increases acidity.

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12
Q

What electron donating groups destabilise the Carboxylate anion and therefore decrease acidity ?

A

E.g. NH2 or OCH3

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13
Q

What determines relative acidic strength among the carboxylic acids ?

A

The inductive effects of the attached groups.

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14
Q

Name four mechanisms by which Carboxylic acids are synthesised ?

A
  1. Oxidative cleavage of alkenes/alkynes
  2. Oxidation of 1º Alcohols and aldehydes
  3. Hydrolysis of Nitriles
  4. Hydroxylation of Grignards or other organometallic reagents
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15
Q

How are tertiary alkyl halides converted into carboxylic acids ?

A

Using Grignard reagents

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16
Q

What is the product if an -OR nucleophile reacts with a carboxylic acid ?

A

An ester

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17
Q

What is the product if a Carboxylic acid reacts with -Cl ?

A

Acid Chloride

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18
Q

What is the product if a Carboxylic acid reacts with NH2 ?

A

An amide

19
Q

What is the general structure of an acid halide ?

A

R-C=O-X

20
Q

Compare the reactivity of Acid halides and Carboxylic acids ?

A

Acid halides are more reactive

21
Q

How can Acyl halides be converted back to carboxylic acids ?

A

Simple hydrolysis with H2O

22
Q

What is the general structure of an acid anhydride ?

A
23
Q

How are acid anhydrides synthesised ?

A

Reaction of an Acyl halide with a Carboxylate salt

24
Q

Describe the relative reactivity of Carboxylic acid derivitives toward nucleophilic acyl substitution ?

A

Amide < Ester < Acid anhydride < Acid chloride

25
Q

Name 6 important reactions of Acid halides ?

A
  1. Friedel-Crafts reaction
  2. Conversion into acids
  3. Conversion into Esters
  4. Conversion into amides
  5. Conversion into alcohols
  6. Synthesis of acid anhydrides
26
Q

Name 4 important reactions of acid anhydrides ?

A
  1. Conversion into acids
  2. Conversion into amides
  3. Conversion into esters
  4. Conversion into alcohols
27
Q

What is the general structure of an amide ?

A
28
Q

Describe the boiling and melting point characteristics of amides ?

A

Unsubstituted and mono-substituted amides form very strong intermolecular hydrogen bonds, and as a result have very high boiling and melting points

29
Q

What is the approximate pH of amides ?

A

Essentially neutral, no acidity compared to Carboxylic acids, and no basicity as compared to amines.

30
Q

Describe Hoffman rearrangement ?

A

Amides can be converted to primary amines with the loss of the Carbonyl carbon

31
Q

Name two important reactions of amides ?

A
  • Conversion into acids
  • Conversion into alcohols
32
Q

What is the general structure of an ester ?

A
33
Q

Explain the boiling point trends displayed by Esters ?

A

Lower than those of comparable acids or alcohols because they are polar molecules but without hydrogens to form hydrogen bonds.

Esters with longer R groups are more non-polar than esters with short side chains

34
Q

What is transesterification ?

A

The process of transforming one ester into another using a nucleophile

35
Q

What is Claisen condensation ?

A

The combination of two ester molecules to form an acetoacetic ester

36
Q

What are fatty acids ?

A

Long chain carboxylic acids

37
Q

What is Saponification ?

A

Fats may be hydrolysed by a base to the components glycerol and the salt of the fatty acid.

The salts of long chain Carboxylic acids are called soaps

38
Q

What are ß-Keto acids ?

A

Carboxylic acids with a keto group at the ß position

39
Q

What is decarboxylation ?

A

When a beta keto acid is heated, the carboxyl group can be readily removed as CO2.

40
Q

Explain Carbonyl reactivity amongst carboxylic acid derivatives ?

A

Acid chlorides > Anhydrides >> Esters > Acids > Amides > Nitriles

41
Q

What is the inductive effect ?

A

The ability of the substituent group, by virtue of its electronegativity, to pull electrons away. This increases the sigma (partially positive) charge of the carbonyl carbon

42
Q

What is the resonance effect ?

A

The ability of the substituent group stabilise the carbocation intermediate by the delocalization of electrons.

43
Q

What is a cyclic ester ? And what is it also known as ?

A

AKA a lactone.

44
Q
A

gamsat march 2016 (26 decks)

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