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funny fun subject > Topic 17: Further Organic > Flashcards

Topic 17: Further Organic Flashcards

1
Q

What is a Chiral molecule?

A

A molecule with a chiral carbon (it is asymmetric)

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2
Q

What is a Chiral Carbon?

A

A carbon atom with four different groups attached to it (asymetric)

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3
Q

How does optical isomerism occur?

A

Results from chiral centres in a molecule with asymmetric carbon atoms

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4
Q

What are optical isomers (properties)?

A
  • non-superimposable mirror images

- rotate the plane of polarisation of plane polarised monochromatic light

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5
Q

Define optical activity?

A

The ability of a single optical isomer to rotate the plane of polarisation of plane- polarised monochromatic light in molecules containing a single chiral centre

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6
Q

What is a racemic mixture?

A

No optical activity due to equal concentrations of two opposite enantiomers

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7
Q

SN1 reaction

A
  • S=Substitution, N=nucleophilic , 1=unimolecular
  • Forms two products
  • It can form a racemic mixture as equal concentrations of opposite enantiomers are formed
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8
Q

SN2 reaction

A
  • S=Substituiton, N=Nucleophillic, 2=bimolecular

- If the molecule is an enantiomer it will reverse the way in which it rotates the polarised light

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9
Q

Define unimolecular (SN1)

A

-1 species involved in the rate-determining step

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10
Q

Define bimolecular

A

-2 species are involved in the rate-determining step

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11
Q

Can Aldehydes and Ketones form Hydrogen bonds with eachother?

A

-No because they do not thave a hydrogen attached to O,N or fluorine

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12
Q

Can Aldehydes and ketones form hydrogen bonds with water?

A

yes

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13
Q

What reagent is used to identify both aldehydes and ketones?

A
  • Brady’s reagent, 2,4-DNP (DiNitroPhenylhydrazine)

- Positive result: Bright Orange Percipitate

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14
Q

How can we identify the carbonyl compound?

A
  • Filter and dry the derivative
  • Measure the melting point of the derivative
  • Compare the value to a data booklet and check which carbonyl compound it belongs too
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15
Q

Acidified Potassium dichromate (VI) test

A
  • Used to distinguish between aldehydes and ketones
  • Colour change from orange to green due to the reduction of the chromium ions
  • Oxidises aldehydes to carboxylic acids
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16
Q

Fehling’s/Benidict’s solution

A
  • Colour change is due to the change from Copper (II) oxide complex to a Copper (I)
  • Positive result Blue -> red precipitate
17
Q

Tollens reagent

A

-Positive result : colourless to a silver mirror

18
Q

How is the Triiodomethane reaction used?

A
  • Carbonyl compound is added to an alkaline solution with iodine
  • To identify the CH3-CO group in aldehydes and ketones and some alcohols
  • Positive result : yellow precipitate
  • Examples : Ethanol, Ethanal, propanone
  • Only one aldehyde gives a positive result (ethanal) and all methyl ketones give a positive result
19
Q

Explain how you would use the triiodomethane test

A
  • Add the carbonyl compound to an alkaline solution of iodine
  • Warm the mixture then cool it
  • If a yellow precipitate is formed there is a CH3CO group present
  • The yellow precipitate is the CHI3 (yellow insoluble solid)
20
Q

Reduction of aldehydes and ketones to alcohols

A
  • Lithium alluminium hydride (LiAlH4)
  • This reagent is dissolved in dry ether along with the carbonyl compound
  • Ketone reduced to a secondary alcohol
  • Aldehyde reduced to primary alcohol [H]
  • Carboxylic acid reduced to primary alcohol 2[H]
21
Q

What is the optical activity when carbonyl compounds react with KCN&HCN and why?

A
  • Most of the time no optical activity (there need to be 2 different groups attached to the carbon)
  • Because the RHC=O is planar and the (: CN) can attack from either side forming two enantiomers
  • This forms a racemic mixture that results in no optical activity
22
Q

What type of reaction is it when you react carbonyl compounds with HCN&KCN?

A

Nucleophilic addition reaction

23
Q

Acidic Hydrolysis of Nitriles

A

R-CN + [H+] + 2H2O -> R-COOH + NH4+

23
Q

Alkaline Hydrolysis of Nitriles

A
  1. R-CN + [OH]- +H2O -> R-COO- + NH3

2. use dilute acid to convert R-COO- into R-COOH

24
Q

Acidic Hydrolysis of esters

A

R1-COO-R2 + H2O ⇌ R1-COOH + R2OH

25
Q

Alkaline Hydrolysis of Esters

A

R1-COO-R2 + NaOH

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