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Chemistry > 11 Aldehydes and Ketones > Flashcards

11 Aldehydes and Ketones Flashcards

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1
Q

What do carbonyl compounds contain?

A

a carbonyl group (C=O)

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2
Q

Give two compounds containing a carbonyl group (C=O).

A

aldehydes

ketones

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3
Q

Compare aldehydes and ketones by:

a) polar carbonyl group
b) how it reacts
c) whether it can be further oxidised

A 
aldehydes:
a) polar carbonyl group RCHO
b) nucleophilic addition
c) can be further oxidised
ketones:
a) polar carbonyl group RCOR'
b) nucleophilic addition
c) cannot be further oxidised
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4
Q

Where is the carbonyl group located in aldehydes as a pose to ketones?

A

in an aldehyde, it is at the end of the carbon chain

in an ketone it is within the carbon chain

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5
Q

State what each of the following represents:

a) C=O
b) CHO
c) R
d) R’

A

a) C=O: carbonyl f.group
b) CHO: aldehyde f.group
c) R = H, alkyl, aryl
d) R’ = alkyl or aryl (can’t be hydrogen)

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6
Q

What is common carbonyl compound formaldehyde manufactured from and used as? State the structure.

(Hint: Meth lab and cadavers)

A

manufactured from methanol
used in many polymers, disinfectant and tissue fixation
(see doc for structure)

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7
Q

What is common carbonyl compound acetaldehyde prepared from and formed in? State the structure.

(Hint: in the body)

A

prepared from ethyl alcohol
formed in the detoxification of alcohol in the liver (=hangover)
(see doc for structure)

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8
Q

What common carbonyl compound forms acetone, where is it excreted and what is it used in? State the structure.

(Hint: makes you smell of pear drops)

A

formed in the human body as a by-product of lipid metabolism
excreted in the urine and breath
laboratory use
(see doc for structure)

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9
Q

Which common carbonyl compound hormones are used? give examples for each. Draw out the structures too.

(Hint: ketone = end in -erone)
(Hint: men are simple/ women more complex and stress hormone is stressful to memorise)
(Hint: makes you smell of pear drops; a popular diet atm)

A

steroid hormones e.g. progesterone, testosterone, cortisone
metabolites e.g. pyruvate, α-ketoglutarate

(see doc for structures)

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10
Q

Which common carbonyl compound are carbohydrates and what are they composed of? Give examples for each. State the structure.

(Hint: each must have 6 C atoms)

A

carbohydrates are composed of polyhydroxy aldehydes or ketones
e.g. glucose and fructose

(see doc for structures)

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11
Q

Describe the bonding in the carbonyl (C=O) bond.

Hint: 1 pi-bond has 2 balloons and unhybridsed bonds are free bonds

A

carbon and oxygen are sp2 hybridised
C=O bond comprises a σ-bond and a π-bond
σ-bond is formed by the overlap of sp2 orbitals of carbon and oxygen
π-bond is formed by the overlap of unhybridised p-orbitals

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12
Q

Describe the bond angle and how electrons are shared in carbonyl (C=O) compounds.

A

bond angles are carbon 120°

electrons in C=O are not shared equally

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13
Q

Describe the electronegativity of the carbonyl (C=O) bond.

A

electronegative oxygen results in polar bond

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14
Q

How would you give an IUPAC name to an aldehyde.

A

IUPAC: the -e in the corresponding alkane is replaced by -al.

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15
Q

How would you give a common name to an aldehyde.

A

derived from the names of corresponding carboxylic acids by replacing -ic acid by -aldehyde.

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16
Q

For each of the following aldehydes state the IUPAC and common names:

a) HCHO
b) CH₃CHO
c) CH₃(CH₂)₂CHO

A 
a)
IUPAC: methanal
Common: formaldehyde 
b) 
IUPAC: ethanal
Common: acetaldehyde 
c) 
IUPAC: butanal
Common: butyraldehyde
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17
Q

How would you give an IUPAC name to a ketone?

A

the -e in the alkane name is replaced with –one.

The location of the group in the chain is indicated by the number before the -one

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18
Q

How would you give a common name to an ketone?.

A

the word ketone is added after naming the alkyl groups attached to the carbonyl group
(not necessarily listed in alphabetical order!)

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19
Q

For each of the following ketones (on the document) state the IUPAC and common names.

A 
a)
IUPAC: Butan-2-one		
Common: Methyl ethyl ketone (MEK)	      
b) 
IUPAC: Propanone
Common: Acetone (dimethyl ketone)
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20
Q

Draw out the general reaction for oxidation of a primary alcohol and state:

a) what is lost
b) the 2 possible chemical reagents
c) the 2 possible biological reagents

A

(see document for diagram)

a) a H atom
b) examples, K₂Cr₂O7 or pyridinium chlorochromate (PCC)
c) Alcohol dehydrogenase + NAD(P)+

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21
Q

Draw out the general reaction for oxidation of a methylaromatic and state the chemical reagent

A

(see document for diagram)

the chemical reagent is H⁺/Na₂Cr₂O7

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22
Q

Draw out the general reaction for the reduction of an acid chloride molecule and state:
a) the 2 possible chemical reagents

(Hint: Li and Al Have over the top Boos x3 OR How Pda is ad Sign Off x4)

A 
(see document for diagram)
a) 
the chemical reagents are: 
LiAlH(OtBu)₃ 
OR H₂, Pd-BaSO₄
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23
Q

Draw out the general reaction for oxidation of a secondary alcohol.

A

(see document for diagram)

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24
Q

Draw out the general Friedel-Crafts acylation (Aryl only) reaction.

A

(see document for diagram)

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25
Q

Draw out the general reaction for ketone synthesis by coupling of an organometallic (“R-”) with a carboxylic acid derivative and state:

a) the reagents
b) draw the general reaction equation

A

a) R’₂CuLi

b) see document

26
Q

Where is the biological version of ketone synthesis by coupling of an organometallic (“R-”) with a carboxylic acid derivative used? Draw out the reaction example.

A

For polyketide and fatty acid biosynthesis

see document for the reaction example

27
Q

State the physical properties of aldehydes/ketones in terms of boiling point.

A

boiling points are affected by the carbon-oxygen double bond is very polar
Higher than ethers (C-O bonds)
Lower than alcohols (hydrogen bonding)

28
Q

State the physical properties of aldehydes/ketones in terms of odour and what is the application of this.

A

Strong and characteristic

Many aldehydes and ketones used as fragrances and flavourings

29
Q

Give 3 examples of ketones/aldehydes used as fragrances and flavourings and draw out their structures.

A

nonanal - roses
vanillin
rasberry ketone
(see document for structures)

30
Q

State and explain the physical properties of aldehydes/ketones in terms of solubility.

A

Similar to alcohols

As carbonyl oxygen forms H-bonds with water

31
Q

State and explain the key concepts of the chemical properties of aldehydes/ketones in terms of their reactions.

A

Carbonyl compounds are unsaturated and polar

Undergo nucleophilic attack resulting in addition to the C=O double bond.

32
Q

Draw the polar charges on the C=O bond.

A

see document

33
Q

Compare for alkenes and carbonyl groups by stating their respective:

a) bond
b) polarity
c) attacked by
d) results

A 
a) 
alkene = C=C
carbonyl = C=O
b)
alkene = non-polar
carbonyl = polar 
c)
alkene = electrophiles
carbonyl = nucleophiles 
d) 
alkene = addition 
carbonyl = addition
34
Q

In which 2 ways can the carbonyl bond also undergo aside from nucleophilic addition?

A

α-substitution

condensation

35
Q

Draw out and describe in 2 steps the mechanism of nucleophilic addition to carbonyl compounds and name the product.

A

Step 1: CN¯ acts as a nucleophile and attacks the slightly positive C. The C=O pi bond breaks; a pair of electrons goes onto the electronegative O.
Step 2: A pair of electrons from O is used to form a bond to H+. Overall, there has been addition of HCN across the double bond.

Product: cyanohydrin
(see document for mechanism)

36
Q

Which compounds readily dissolve in water and do they form?

A

Formaldehyde dissolves readily in water
Acetaldehyde somewhat also
form hydrates

37
Q

Draw out the general hydration reaction for formaldehyde and state:

a) the reagent
b) draw the general reaction equation
c) the type of reaction and what it forms

A

a) addition of water (H₂O)
b) see document
c) nucleophilic addition, forms hydrates

38
Q

Fill in the following table with the products and intermediates and their names for the reactions between aldehydes/ketones and alcohols twice?

A

see document

39
Q

Give 2 examples of mixed acetals are present in biological strcutures.

(Hint: ultrastrcuture of plants and animals)

A

DNA

Cellulose

40
Q

What is the biological relevance of ketones/aldehydes?

A

sugars - i.e. glucose and fructose

41
Q

State the 3 stages of oxidation of primary alcohols.

A

primary alcohol → aldehyde → carboxylic acid

42
Q

State the 3 stages of oxidation of secondary alcohols.

A

secondary alcohol → ketone → no more oxidation

43
Q

State the oxidising agents used for oxidising alcohols:

a) chemically
b) biologically

A

a) chromate or permanganate oxidising agent

b) Aldehyde dehydrogenase (ALDH) + NAD(P)+

44
Q

What is the lab test for aldehydes?

A

chromate or permanganate oxidising agent changing from green to orange

45
Q

What is the Tollen’s reagent test?

A

Aldehyde → Carboxylic acid
Silver mirror formed from a clear solution
Tollens reagent = silver nitrate (AgNO₃), aqueous ammonia (NH₃ (ag)), NaOH

46
Q

Write out the (balanced) Tollen’s reagent test equation.

A

see document

47
Q

What is Benedict’s reagent test for reducing sugars? (Hint = in alphabet B then C)

A

Benedict’s reagent = CuSO4 + alkaline citrate

Solution changes from blue to brick red

48
Q

What is the Fehling’s reagent test for reducing sugars?

A

Fehling’s reagent = CuSO4 + alkaline tartrate

Solution changes from blue to brick red

49
Q

How do you know if a sugar is a reducing sugar from its structure?

A

Has C=O bond in it

50
Q

Write out the (balanced) Fehling’s/Benedict’s reagent test equation

A

see document

51
Q

State how aldehyde and ketone reductions occur:

a) what is needed?
b) chemically (the different possible reagents)
c) biologically

A

a) Need Source of H₂ or H-/H+
b) NaBH4, LiAlH4, Diisobutylaluminium hydride (DIBAL); H2 and Pd/Pt/Ni
c) NAD(P)H

52
Q

Draw out the mechanism for aldehyde/ketone reduction including curly arrows.

A

see document

53
Q

What are the two types of α-substitutions that can occur?

A

Aldol addition + condensation

54
Q

What do aldehydes/ketones undergo with themselves?

A

Undergo self-addition in the presence of an acid or base (or enzyme)

55
Q

Draw out the 3-stage self-addition reaction equation for the self-addition of acetaldehyde.

A

see document

56
Q

Draw out the mechanism of the self-addition of acetaldehyde and state the molecules involved.

A

see document

Mechanism involves enol or enolate

57
Q

What is an enolate?

A

R=C(O-)H

58
Q

Describe the electronic properties of an enolate molecule.

A

Electron density on O and C
Act as a carbon nucleophile
(see document for the diagram)

59
Q

State and draw out the 2 examples of biological carbon-carbon bond formation.
(Hint: first stack together and then opposite splitting)

A

Carbohydrate metabolism - aldolases

see document for them

60
Q

State a medical example for testing for ketones and how do they work?

A

Urinalysis sticks used by diabetics and dieters

Work by an enolate reaction

61
Q

State the ketone reaction for urinalysis sticks to work and the enzymes.

A

see document

Chemistry (12 decks)

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