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Chemistry Module 6 > Carbonyls > Flashcards

Carbonyls Flashcards

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1
Q

Is there any numbers when naming aldehydes?

A

Only when di

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2
Q

When is there numbers in ketones?

A

When the chain is more than 5 carbons/when it’s di

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3
Q

What must you remember when it’s di?

A

Must keep the e before the number

eg pentane-2,4-dione or butane-1,4-dial

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4
Q

What is the general formula of carbonyls?

A

CnH2nO

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5
Q

How do you describe pi bonds for C-O?

A

P orbitals on adjacent carbon and oxygen atoms overlap sideways forming a pi bond above and below the line between the nuclei of the bonded atoms

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6
Q

What are some features of the C-O pi bond?

A

Localised electrons
High electron density
Reacts with nucleophiles because polar bond means Cdelta+ attracts them

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7
Q

What reactions can the C=O do?

A 
Addition (double bond)
Nucleophilic addition (Cdelta+ attracts nucleophiles)
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8
Q

What reagent tests for primary/secondary alcohols, aldehydes and methanoic acid?

A

H+/Cr₂O₇²⁻

Heat

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9
Q

What does H+/Cr₂O₇²⁻ and heat test for?

A

Primary/secondary alcohols, aldehydes and methanoic acid

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10
Q

Why does H+/Cr₂O₇²⁻ test for methanoic acid but no other carboxylic acids?

A

There’s 1 H on the C in the functional group bit in methanoic acid

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11
Q

What is the positive result from H+/Cr₂O₇²⁻

A

Orange solution goes to a green solution

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12
Q

What does the reagent 2,4-DNPH and sulfuric acid test for?

A

C=O in aldehydes and ketones

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13
Q

What reagent tests for C=O in aldehydes/ketones?

A

2,4-Dinitrophenylhydrazine (2,4-DNPH)

Sulfuric acid

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14
Q

What is the positive result for 2,4-DNPH?

A

Yellow/orange precipitate

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15
Q

What does the reagent Tollen’s and heat test for?

A

Aldehydes

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16
Q

What tests for just aldehydes?

A

Tollen’s and heat

17
Q

What is the positive result for Tollen’s?

A

Silver mirror will form

18
Q

What is the equation for H+/Cr₂O₇²⁻?

A

6e⁻ + Cr₂O₇²⁻ + 14H⁺ -> 2Cr³⁺+7H₂O

19
Q

How do you use the colour of H+/Cr₂O₇²⁻ to prove something has been oxidised?

A

Cr₂O₇²⁻ is green and Cr³⁺ is orange and it has been reduced.

In order for it to be reduced something else must have been oxidised.

20
Q

How do you make ammoniacal silver nitrate?

A 
Mix AgNO₃ + NaOH -> Brown ppt Ag₂O
Dissolve ppt in NH₃ to make Tollen's
Mix aldehyde + Tollen's + heat
Aldehyde goes to silver mirror
Ag⁺(aq) +e- gets reduced to Ag(s)
Aldehyde gets oxidised to carboxylic acid
21
Q

What is the equation for Tollen’s?

A

Ag⁺(aq) + e- -> Ag(s)

22
Q

How do you distinguish between the precipitates made by 2,4-DNPH?

A 
Use the melting point of 2,4-DNPH derivative
Filter (impure)
Recrystalise (purify)
Filter
Leave to dry
Collect melting point
Compare to a database of known values
23
Q

What are ketones reduced to?

A

Secondary alcohols

24
Q

What are aldehydes reduced to?

A

Primary alcohols

25
Q

What reagent is used to reduce carbonyls?

A

NaBH₄

never in equations - Source of H-/hydrides

26
Q

What mechanism is done with carbonyls?

A

Nucleophilic addition

27
Q

How do you make HCN?

A

In situ

NaCN + H₂SO₄ -> HCN + NaHSO₄

28
Q

What is used to do the nucleophilic addition mechanisms?

A

H- + water

-CN + H+

Chemistry Module 6 (10 decks)

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