12 Carboxylic Acids Flashcards
What is the carboxylic acid group?
consists of C=O and -OH bonded to the same carbon
Where does the name ‘carboxyl’ group come from?
CARBonyl (C=O)
hydrOXYL (-OH)
Draw an aliphatic and an aromatic carboxylic acid.
see document
Define:
a) aliphatic acid
b) aromatic acid
a) -COOH bonded to an alkyl group
b) -COOH bonded to an aryl group
What are long chain monocarboxylic acids called?
fatty acids
Describe the bond angle due to the bonding due to the C=O bond eclipsed with O-H?
Carbon and both oxygens are sp2 hybridized.
Bond angles are close to 120°
O-H eclipsed with C=O
State the 2 bond lengths (C=O and C-O) and the bond angle that is shown on the document.
C=O = 1.21A
C-O = 1.36A
see document
Draw the orbital-diagrams for a general carboxylic acid.
see document
State the IUPAC process of naming carboxylic acids.
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
How are aromatic carboxylic acids named (in the IUPAC method)?
Aromatic carboxylic acids are also named after the parent compound
e.g. Benzoic acid (benzene)
State the process for the naming of common carboxylic acids.
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
Define ‘ester.’
Derivatives of carboxylic acids where alcohol replaces the OH group
State the IUPAC process of naming esters.
First name the alkyl from the alcohol -yl
Then name the acid (with the C=O) -oate
Give the IUPAC and common name of the ester shown on the document and state the alcohol and carboxylic acid that forms it.
IUPAC = ethyl ethanoate
Common = ethyl acetate
alcohol - ethanol
acid - acetic/ethanoic acid
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) K₂Cr₂O₇ OR KMnO₄
b) RC=O
c) see document
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) ADH, ALDH OR NAD(P)⁺
b) RC=O
c) see document
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) K₂Cr₂O₇ OR KMnO₄
b) see document
For the reaction of chemically obtaining a carboxylic acid via hydrolysis, state the reagent needed.
use acid or base
For the reaction of biologically obtaining a carboxylic acid via hydrolysis, state the reagent and enzyme needed.
esterases and water
Give 2 biological examples of obtaining carboxylic acids via hydrolysis.
Lipases: produced in the pancreas – digestion of fats
acetylcholine → acetic acid + choline
(H₂O and acetylcholinesterase)
see document
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) step 1: NaCN, step 2: H₃O⁺
b) R-C-C≡N
c) see document
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) step 1: R-⁺MgBr, step 2: H₃O⁺
b) see document
c) RC=O-MgBr⁺
d) see document
Give a biological example of a reaction for chemically obtaining carboxylic acids via Grignard reagents and the enzyme used. (draw the structures)
ribulose-1,5-biphosphate → enol → carboxylic acid
(see document)
Rubisco = biotin-dependent carboxylases
In terms of the physical properties and bonds, state and explain the solubility of carboxylic acids.
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
In terms of the physical properties and bonds, state and explain the boiling points of carboxylic acids.
Low molecular weight carboxylic acids have high boiling points
Strong intermolecular bonds
Form dimers by hydrogen bonding
Draw a carboxylate salt with a sodium ion in it.
see document
What do carboxylic acids form?
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)
In terms of the physical properties and bonds, what type of acids are carboxylic acids?
weak acid partial dissociation (reversible arrow) ⇌
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.
see document
the charge is delocalised over 3 atoms
pi-system
stable anion if formed
What happens to the pKa of a carboxylic acid as carbon chain length increases?
the pKa increases (less dissociation)
see document for graph
Explain the role and properties of the following groups within the carboxylic acid:
a) alcohol (-OH)
b) carbonyl (C=O)
a) leaving group for substitution reactions
b) (positive carbon-centre) attacked by nucleophiles
What is a condensation reaction with a carbonyl also known as?
nucleophilic acyl substitution
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).
see document
For the reaction to chemically obtain an acid chloride from a carboxylic acid, state:
a) the 3 possible reagents
b) the reaction equation
a) SOCl₂ OR PCl₃ OR PCl₅
b) see document
Why is it useful to synthesise acid chlorides.
more reactive than the acid
useful for synthesis of amides, esters etc…
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) ROH (alcohol) and H⁺
b) see document
c) H₂O
d) esterification
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) glutamate
b) glutamate synthetase and ATP
c) see document
d) esterification
For the reduction of a carboxylic acid, state:
a) what needs to be added
b) the reagent
c) the reaction equation
a) add H- ions
b) LiALH₄
c) see document
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) Claisen reaction
b) RC=O-SCoA and OC=O-C-C=OSCoA
c) synthase
d) see document
e) Reversible reaction
What is the RC=O-SCoA converted into?
(−)C=O-SCoA
Why is a thioester used instead of a carboxylic acid in C-C bond formation?
thioester is more reactive than a carboxylic acid
What is the Claisen reaction used for biologically and what does it allow?
Fatty acid and polyketide biosynthesis
allows loss of 2-carbon unit from FAs
Describe the acid hydrolysis of an ester, state:
a) the reagents
b) the reaction equation for ethyl methanoate
Esters react with water and an acid catalyst yielding a carboxylic acid and alcohol
a) H⁺ (from an acid) and H₂O
b) see document
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
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
What are fatty acids?
Long hydrocarbon chain monocarboxylic acids
Define:
a) Saturated fatty acids
b) Unsaturated fatty acids
a) no double bonds
b) contain one (mono-) or more (poly-unsaturated) alkenes
Which alkenes are naturally-occurring?
Cis-alkenes
What do trans alkenes often result from chemically?
from isomerising the double bond during hydrogenation
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) 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
What is arachidonic acid the precursor to?
many prostaglandins – biological signalling molecules
What are fatty acids the components of?
Triacylglycerols and Glycerophospholipids
What are Triacylglycerols?
fats and oils
What are Glycerophospholipids?
cell membranes
Draw out the equation for triglyceride formation.
see document
Why are glycerophospholipids useful?
to maintain the fluid environment of cell membranes
hydrophilic heads on the outside and hydrophobic tails inwards to create a hydrophobic core
Draw out and label the structure of a single phospholipid with glycerol within its stricture.
see document
Draw out the structure of glycerol choline.
see document
What are soaps in terms of carboxylic acids?
sodium or potassium salts of fatty acids.
What are detergents in terms of carboxylic acids and how does their structure remove stains?
Sulfate salts
Hydrophobic tails dissolve in grease/dirt.
Polar heads point out making particles water soluble
What is shown in the picture on the document?
a soap
Label the fat-soluble and water-soluble on the following molecule.
see document
Where are bile acids/salts biosynthesised?
Biosynthesised from cholesterol in the liver.
What do bile acids/salts allow in the body and how?
Allow absorption of fats and fat-soluble vitamins from the small intestine by acting as detergents.
Draw out the 3-stage conversion of cholesterol into (carboxylic acid) glycocholic acid naming the intermediate product too.
cholesterol → cholic acid → glycocholic acid
see document
For both ‘aryl’ and ‘phenyl’ groups, state the:
a) definition
b) formation
c) number of carbon atoms
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
From the structures a) and b) shown on the document, distinguish between phenyl and aryl.
a) aryl (double bond is on the right of the R-group)
b) phenyl (double bond is on the left of the R-group)
