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Chemistry Y13 > Aldehydes & Ketones > Flashcards

Aldehydes & Ketones Flashcards

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1
Q

How do we DISTINGUISH between ALDEHYDES & KETONS?

A
  • Aldehydes can be OXIDISED into CARBOXYLIC ACIDS
  • Ketones CANNOT be OXIDISED into a CARBOXYLIC ACID
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2
Q

Why can ALDEHYDES be OXIDISED into CARBOXYLIC ACIDS?

A

There is a HYDROGEN ATTACHED to the CARBONYL GROUP

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3
Q

How do we OXIDISE KETONES?

A
  • We would have to BREAK the C-C BOND
  • So they are NOT EASILY OXIDISED
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4
Q

How come there is a COLOUR CHANGE with OXIDATION reactions of ALDEHYDES?

A
  • As an ALDEHYDE is oxidised, another compound is REDUCED
  • So a REAGENT is used which causes the COLOUR CHANGE
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5
Q

What are the 2 REAGENTS that can be used to DISTINGUISH between ALDEHYDES & KETONES?

A
  • Tollens’ Reagent
  • Fehlings’ Solution
  • KETONES DO NOT REACT WITH EITHER
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6
Q

What is TOLLENS’ REAGENT?

A
  • COLOURLESS solution of SILVER NITRATE
  • DISSOLVED in NH3(aq)
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7
Q

What VISIBLE OBSERVATION can be made when TOLLENS’ REAGENT reacts with an ALDEHYDE?

A
  • If HEATED in a test tube with an ALDEHYDE
  • A SILVER MIRROR is formed after a few minutes
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8
Q

What is FEHLINGS’ SOLUTION?

A
  • A BLUE SOLUTION of complexed COPPER IONS (Cu II)
  • DISSOLVED in NaOH
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9
Q

What VISIBLE OBSERVATION can be made when FEHINGS’ SOLUTION reacts with an ALDEHYDE?

A
  • If HEATED with an ALDEHYDE the Cu2+ is REDUCED
  • To a BRICK RED PRECIPITATE of Cu+O
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10
Q

How would you NOT HEAT KETONES & ALDEHYDES in a REACTION and why?

A
  • NOT using NAKED FLAME
  • Because both are FLAMMABLE
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11
Q

What can PRIMARY ALCOHOLS be OXIDISED into?

A

Primary Alcohol —> Aldehyde —> Carboxylic Acid

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12
Q

What can SECONDARY ALCOHOLS be OXIDISED into?

A

Secondary Alcohol —> Ketones

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13
Q

What are ALDEHYDES & KETONES?

A
  • CARBONYL GROUPS
  • With the FUNCTIONAL GROUP C=O
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14
Q

What is the GENERAL FORMULA for ALDEHYDES & KETONES?

A

Cn + H2n + O

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15
Q

What is the GENERAL FORMULA for CARBOXYLIC ACIDS?

A

Cn + H2N+1

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16
Q

What INTERMOLECULAR FORCES holds ALDEHYDES and KETONES together?

A
  • The presence of CARBONYL groups means that there are VAN DE WAALS forces
  • But also PERMANENT DIPOLE-DIPOLE interactions
17
Q

What INTERMOLECULAR FORCES holds ALCOHOLS together?

A
  • Van De Waals
  • Permanent Dipole-Dipole Interactions
  • Hydrogen Bonding
18
Q

Describe the SOLUBILITY of ALDEHYDES and KETONES

A
  • Although they CANNOT form H-BONDS with other CARBONYL compounds
  • The O- can use its LONE PAIR to form a H-BOND with the H atoms in WATER
  • ALL aldehydes and ketones CAN DISSOLVE in ORGANIC SOLVENTS
19
Q

What VISIBLE OBSERVATION can you make when K2CR2O7 OXIDISES an ALDEHYDE or 1o ALCOHOL?

A

Orange —> Green

20
Q

What is one reason why TOLLENS’ REAGENT is used as an [O] for ALDEHYDES rather than K2CR2O7?

A

It produces a CLEARER VISIBLE CHANGE

21
Q

What can CARBOXYLIC ACIDS be REDUCDED into?

A

Carboxylic Acid —> Aldehyde —> Primary Alcohol

22
Q

What can KETONES be REDUCED into?

A

Ketones —> Secondary Alcohols

23
Q

What TWO SOLUTIONS are in FEHLING’S SOLUTION?

A
  • FEHLING’S A - Contains Cu2+ (Blue)
  • FEHLING’S B - Complexing agent that can form DATIVE BONDS with metal atoms / ions
24
Q

When ALDEHYDES react with FEHLING’S SOLUTION, what is OXIDISED and what is REDUCED into what?

A
  • Cu2+ is REDUCED into Cu+
  • Aldehydes OXIDISE into CARBOXYLIC ACIDS
25
Q

When ALDEHYDES react with TOLLEN’S REAGENT, what is OXIDISED and what is REDUCED into what?

A
  • Ag+ is REDUCED
  • Aldehydes are OXIDISED into CARBOXYLIC ACIDS
26
Q

What can PRIMARY ALCOHOLS be OXIDISED to?

A

Primary Alcohol —> Aldehyde —> Carboxylic Acid

27
Q

What can SECONDARY ALCOHOLS be OXIDISED into?

A

Secondary Alcohols —> Ketone

28
Q

What 3 OXIDISING AGENTS can be used for ALDEHYDES and ALCOHOLS?

A
  • K2Cr2O7
  • Tollens’ Reagent
  • Fehling’s Solution
29
Q

What can CARBOXYLIC ACIDS be REDUCED into?

A

Carboxylic Acids —> Aldehydes —> Alcohols

30
Q

What are 2 REDUCING AGENTS that can be used for KETONES and CARBOXYLIC ACIDS?

A
  • LiAlH4 (Lithium Tetra-Hydrido-Aluminate)
  • NaBH4 (Sodium Tetra-Hydrido-Borate)
31
Q

What is the DIFFERENCE between LiAlH4 and NaBH4?

A

LiAlH4 is MORE REACTIVE than NaBH4

32
Q

If it is a REDUCTION, what MECHANISM is used?

A

Nucleophillic Addition

33
Q

Why can LiAlH4 and NaBH4 be used as REDUCING AGENTS?

A
  • They generate HYDRIDE IONS
  • Which are NUCLEOPHILES
34
Q
A

Chemistry Y13 (4 decks)

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