17b - carbonyl compounds Flashcards

1
Q

what are carbonyls?

A

compounds with c=o bonds

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2
Q

what are the trend in solubility of carbonyls with chain length?

A

higher chain length = lower solubility
- smaller carbonyls could H-bond with water as they have similar intermolecular forces)
- stronger london forces as chain length increases (which outweighs? H2O)

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3
Q

what is the trend in boiling point with increasing chain length?

A

higher chain length = higher bp
- stronger IM forces

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4
Q

what are the conditions and reagents of oxidation of aldehydes? what is the product?

A

carboxylic acid
- heat under reflux
- K2Cr2O7 & dilute H2SO4

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5
Q

what would be the observations of oxidation of aldehydes?

A

orange Cr2O7(2-) reduced to green Cr3(3+)

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6
Q

what compound could be tested with fehling’s solution? state the conditions, reagents & observation.

A

aldehydes
condition: heat gently
reagents: solution with Cu2+ ions
observation: Cu2+ ions reduced to CuO (red ppt)
(& aldehydes oxidised to carboxylic acids)

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7
Q

what compound could be tested with tollen’s reagent? state the conditions, reagents & observation.

A

aldehydes
condition: heat gently
reagents: aq, NH3 + AgNO3 -> complex ion [Ag(NH3)2]+
observation: silver mirror forms as Ag+ (aq) reduced to Ag(s))
(& aldehydes oxidised to carboxylic acids)

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8
Q

what is the reagents & conditions of reduction of carbonyls?

A

reagents: LiAlH4 in dry ether / reduction agent
conditions: room temp. & Pa

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9
Q

what would aldehydes & ketones be reduced to?

A

aldehyde: primary alcohols
ketones: secondary alcohols

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10
Q

what are the general formulas of reduction of carbonyls?

A

R-CHO + 2[H] -> R-COOH
R1-CO-R2 + 2[H] -> R1-CH(OH)-R2

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11
Q

what are formed with nucleophillic addition of carbonyls?

A

hydroxynitriles

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12
Q

what are the reagents & conditions of nucleophillic addition of carbonyls? draw the mechanism.

A

reagent: HCN in presence of KCN
conditions: room temp. & Pa

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13
Q

what is the KCN used for in nucleophillic addition of carbonyls?

A

extra KCN increases concentration of CN- ion as nucleophile needed

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14
Q

why would a mixture of enantiomers be produced from addition of carbonyls?

A

CN- could attack both sides

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15
Q

what does 2,4-dnph test for? what observation will be formed?

A

C=O bond in carbonyls, forms bright orange ppt

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16
Q

how could different carbonyl compounds be identified from the 2,4-dnph test?

A
  • orange ppt are different derivatives of carbonyl compounds
    -> identify melting point after purification by recrystallisation & compare to database
17
Q

what is the iodoform test specifically for?

A

carbonyls with methyl group attached next to C=O (ethanal / methyl ketones)

18
Q

what are the reagents & conditions of the iodoform test?

A

reagents - I2 with NaOH (alkali)
conditions - warm gently

19
Q

what is formed in the iodoform test? state the formula and the observations.

A

CHI3, triiodomethane
yellow ppt