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Chemistry > 12 Carboxylic Acids > Flashcards

12 Carboxylic Acids Flashcards

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1
Q

What is the carboxylic acid group?

A

consists of C=O and -OH bonded to the same carbon

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2
Q

Where does the name ‘carboxyl’ group come from?

A

CARBonyl (C=O)

hydrOXYL (-OH)

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3
Q

Draw an aliphatic and an aromatic carboxylic acid.

A

see document

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4
Q

Define:

a) aliphatic acid

b) aromatic acid

A

a) -COOH bonded to an alkyl group

b) -COOH bonded to an aryl group

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5
Q

What are long chain monocarboxylic acids called?

A

fatty acids

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6
Q

Describe the bond angle due to the bonding due to the C=O bond eclipsed with O-H?

A

Carbon and both oxygens are sp2 hybridized.
Bond angles are close to 120°
O-H eclipsed with C=O

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7
Q

State the 2 bond lengths (C=O and C-O) and the bond angle that is shown on the document.

A

C=O = 1.21A
C-O = 1.36A
see document

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8
Q

Draw the orbital-diagrams for a general carboxylic acid.

A

see document

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9
Q

State the IUPAC process of naming carboxylic acids.

A

Select the longest carbon chain containing the carboxyl group. The -e ending of the parent alkane name is replaced by the suffix -oic acid.
e.g. HCOOH Methanoic acid, CH₃COOH Ethanoic acid

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10
Q

How are aromatic carboxylic acids named (in the IUPAC method)?

A

Aromatic carboxylic acids are also named after the parent compound
e.g. Benzoic acid (benzene)

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11
Q

State the process for the naming of common carboxylic acids.

A

End in –ic acid. e.g. HCOOH Formic acid, CH₃COOH Acetic acid etc.
Often derived from Latin or Greek word indicating the original source or properties of the acid

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12
Q

Define ‘ester.’

A

Derivatives of carboxylic acids where alcohol replaces the OH group

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13
Q

State the IUPAC process of naming esters.

A

First name the alkyl from the alcohol -yl

Then name the acid (with the C=O) -oate

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14
Q

Give the IUPAC and common name of the ester shown on the document and state the alcohol and carboxylic acid that forms it.

A

IUPAC = ethyl ethanoate
Common = ethyl acetate
alcohol - ethanol
acid - acetic/ethanoic acid

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15
Q

For the 2 stage reaction of chemically obtaining carboxylic acids via oxidation of an alcohol and state:

a) the 2 possible reagents
b) the intermediate product (or first product)
c) the reaction equation

A

a) K₂Cr₂O₇ OR KMnO₄
b) RC=O
c) see document

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16
Q

For the 2 stage reaction of biologically obtaining carboxylic acids via oxidation and state:

a) the 2 possible reagents
b) the intermediate product (or first product)
c) the reaction equation

A

a) ADH, ALDH OR NAD(P)⁺
b) RC=O
c) see document

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17
Q

For the reaction of chemically obtaining a carboxylic acid via oxidation of a substituted aromatic state:

a) the 2 possible reagents
b) the reaction equation

A

a) K₂Cr₂O₇ OR KMnO₄

b) see document

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18
Q

For the reaction of chemically obtaining a carboxylic acid via hydrolysis, state the reagent needed.

A

use acid or base

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19
Q

For the reaction of biologically obtaining a carboxylic acid via hydrolysis, state the reagent and enzyme needed.

A

esterases and water

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20
Q

Give 2 biological examples of obtaining carboxylic acids via hydrolysis.

A

Lipases: produced in the pancreas – digestion of fats
acetylcholine → acetic acid + choline
(H₂O and acetylcholinesterase)
see document

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21
Q

For the 2 stage reaction for chemically obtaining carboxylic acids via a bromoalkane, state:

a) the reagent for each stage
b) the intermediate product (or first product)
c) the reaction equation

A

a) step 1: NaCN, step 2: H₃O⁺
b) R-C-C≡N
c) see document

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22
Q

For the 2 stage reaction for chemically obtaining carboxylic acids via Grignard reagents, state:

a) the reagents
b) draw the mechanism for the first stage (curly arrows)
c) the intermediate product (or first product)
d) the reaction equation

A

a) step 1: R-⁺MgBr, step 2: H₃O⁺
b) see document
c) RC=O-MgBr⁺
d) see document

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23
Q

Give a biological example of a reaction for chemically obtaining carboxylic acids via Grignard reagents and the enzyme used. (draw the structures)

A

ribulose-1,5-biphosphate → enol → carboxylic acid
(see document)
Rubisco = biotin-dependent carboxylases

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24
Q

In terms of the physical properties and bonds, state and explain the solubility of carboxylic acids.

A

Carboxylic acid group - hydrogen bonds to water molecules
Carboxylate salt – ion-dipole interactions
Larger saturated alkyl groups are not water-soluble as they are waxy, odourless solids with Van der Waal’s forces

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25
Q

In terms of the physical properties and bonds, state and explain the boiling points of carboxylic acids.

A

Low molecular weight carboxylic acids have high boiling points
Strong intermolecular bonds
Form dimers by hydrogen bonding

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26
Q

Draw a carboxylate salt with a sodium ion in it.

A

see document

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27
Q

What do carboxylic acids form?

A

Form dimers by hydrogen bonding
A dimer is an oligomer consisting of two monomers joined by bonds that can be either strong or weak, covalent or intermolecular (see document)

28
Q

In terms of the physical properties and bonds, what type of acids are carboxylic acids?

A 
weak acid
partial dissociation (reversible arrow) ⇌
29
Q

Write out the equation for the dissociation of methanoic acid including the pKa of the acid and state how the charge is distributed in a carboxylic acid.

A

see document
the charge is delocalised over 3 atoms
pi-system
stable anion if formed

30
Q

What happens to the pKa of a carboxylic acid as carbon chain length increases?

A

the pKa increases (less dissociation)

see document for graph

31
Q

Explain the role and properties of the following groups within the carboxylic acid:

a) alcohol (-OH)
b) carbonyl (C=O)

A

a) leaving group for substitution reactions

b) (positive carbon-centre) attacked by nucleophiles

32
Q

What is a condensation reaction with a carbonyl also known as?

A

nucleophilic acyl substitution

33
Q

Draw out the 3-step general addition-elimination mechanism using X as the -OH group and Nu as the nucleophile (include curly arrows, charges and electrons).

A

see document

34
Q

For the reaction to chemically obtain an acid chloride from a carboxylic acid, state:

a) the 3 possible reagents
b) the reaction equation

A

a) SOCl₂ OR PCl₃ OR PCl₅

b) see document

35
Q

Why is it useful to synthesise acid chlorides.

A

more reactive than the acid

useful for synthesis of amides, esters etc…

36
Q

For the reaction to chemically obtain an ester from a carboxylic acid, state:

a) the 2 reagents
b) the reaction equation
c) the single by-product
d) what the reaction is known as

A

a) ROH (alcohol) and H⁺
b) see document
c) H₂O
d) esterification

37
Q

For the reaction to biologically obtain an ester from a carboxylic acid, state:

a) the 2 reagents
b) the reaction equation
c) the single by-product
d) what the reaction is known as

A

a) glutamate
b) glutamate synthetase and ATP
c) see document
d) esterification

38
Q

For the reduction of a carboxylic acid, state:

a) what needs to be added
b) the reagent
c) the reaction equation

A

a) add H- ions
b) LiALH₄
c) see document

39
Q

For the C-C bond formation from a thioester to form a ketone, state:

a) what the reaction is also known as
b) the reagents
c) the enzyme
d) the reaction equation
e) the type of reaction

A

a) Claisen reaction
b) RC=O-SCoA and OC=O-C-C=OSCoA
c) synthase
d) see document
e) Reversible reaction

40
Q

What is the RC=O-SCoA converted into?

A

(−)C=O-SCoA

41
Q

Why is a thioester used instead of a carboxylic acid in C-C bond formation?

A

thioester is more reactive than a carboxylic acid

42
Q

What is the Claisen reaction used for biologically and what does it allow?

A

Fatty acid and polyketide biosynthesis

allows loss of 2-carbon unit from FAs

43
Q

Describe the acid hydrolysis of an ester, state:

a) the reagents
b) the reaction equation for ethyl methanoate

A

Esters react with water and an acid catalyst yielding a carboxylic acid and alcohol

a) H⁺ (from an acid) and H₂O
b) see document

44
Q

Describe the basic hydrolysis of an ester, state:

a) the reagents
b) the reaction equation for ethyl methanoate
c) the 2 possible products
d) the other name for base hydrolysis

A

Esters react with bases to produce the salt of the carboxylic acid and alcohol

a) NaOH (or another alkali)
b) see document
c) salt (HC=O-O-⁺Na) or carboxylic acid (HC=O-OH)
d) saponification

45
Q

What are fatty acids?

A

Long hydrocarbon chain monocarboxylic acids

46
Q

Define:

a) Saturated fatty acids

b) Unsaturated fatty acids

A

a) no double bonds

b) contain one (mono-) or more (poly-unsaturated) alkenes

47
Q

Which alkenes are naturally-occurring?

A

Cis-alkenes

48
Q

What do trans alkenes often result from chemically?

A

from isomerising the double bond during hydrogenation

49
Q

Identify the different names and draw out the fatty acids for each of the following melting points:

a) -50°C
b) -9 °C
c) 13°C
d) 46.5
e) 43°C
f) 76°C

(ALEOLA)

A

a) Archadonic acid OR 20:4 cis,cis,cis,cis-Δ5Δ8,Δ11,Δ14 OR n-6
b) Linoleic acid
c) Oleic acid OR 18:1 cis-Δ9 OR n-9
d) Elaidic acid OR 18:1 trans-Δ9 OR n-9
e) Lauric acid
f) Arachidic acid

50
Q

What is arachidonic acid the precursor to?

A

many prostaglandins – biological signalling molecules

51
Q

What are fatty acids the components of?

A

Triacylglycerols and Glycerophospholipids

52
Q

What are Triacylglycerols?

A

fats and oils

53
Q

What are Glycerophospholipids?

A

cell membranes

54
Q

Draw out the equation for triglyceride formation.

A

see document

55
Q

Why are glycerophospholipids useful?

A

to maintain the fluid environment of cell membranes

hydrophilic heads on the outside and hydrophobic tails inwards to create a hydrophobic core

56
Q

Draw out and label the structure of a single phospholipid with glycerol within its stricture.

A

see document

57
Q

Draw out the structure of glycerol choline.

A

see document

58
Q

What are soaps in terms of carboxylic acids?

A

sodium or potassium salts of fatty acids.

59
Q

What are detergents in terms of carboxylic acids and how does their structure remove stains?

A

Sulfate salts
Hydrophobic tails dissolve in grease/dirt.
Polar heads point out making particles water soluble

60
Q

What is shown in the picture on the document?

A

a soap

61
Q

Label the fat-soluble and water-soluble on the following molecule.

A

see document

62
Q

Where are bile acids/salts biosynthesised?

A

Biosynthesised from cholesterol in the liver.

63
Q

What do bile acids/salts allow in the body and how?

A

Allow absorption of fats and fat-soluble vitamins from the small intestine by acting as detergents.

64
Q

Draw out the 3-stage conversion of cholesterol into (carboxylic acid) glycocholic acid naming the intermediate product too.

A

cholesterol → cholic acid → glycocholic acid

see document

65
Q

For both ‘aryl’ and ‘phenyl’ groups, state the:

a) definition
b) formation
c) number of carbon atoms

A

aryl:

a) always contains an aromatic ring
b) when H is lost from an aromatic group
c) Different number depending on the group

phenyl:

a) derived from benzene by removal of 1 H atom
b) when H is lost from a benzene group
c) can only have 6 groups

66
Q

From the structures a) and b) shown on the document, distinguish between phenyl and aryl.

A

a) aryl (double bond is on the right of the R-group)

b) phenyl (double bond is on the left of the R-group)

Chemistry (12 decks)

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