Carbonyls

Question 1

Carbonyl

Answer 1

Carbon double bonded to Oxygen C=O
- present in Aldehydes,Ketones, Carboxylic acids + Amides

Question 2

Example of difference between Aldehydes + Ketones

Answer 2

Aldehydes have C=O at end
Ketones have C=O in middle

Question 3

Are Aldehydes and Ketones soluable in Water

Answer 3

Yes
Can form Hydrogen bonds with Water due to Electronegative Oxygen

As carbon chain increase they become less soluble

Question 4

Is the boiling point of aldehydes + Ketones higher or lower than corresponding Alcohol + Carboxylic Acid

Answer 4

Lower
A + K cannot Hydrogen bond with each other = relies on Dipole-Dipole + London Forces

Question 5

3 elements which can hydrogen bond

Answer 5

Fluorine oxygen Nitrogen

Question 6

What do Aldehydes and ketones look and smell like

Answer 6

Colourless liquid + Fruity smell

Question 7

What are the 3 tests for carbonyls

Answer 7

Feelings
Tollen’s reagent
2,4 DNPH Solution

Aldehydes give + results for all and ketones give negative results for all except 2,4 DNPH

Question 8

Conditions for fehlings test and positive results

Answer 8

Mix Fehlings A + B and Warm

Blue to Brick red
Due to Cu2+ to Cu+

Question 9

Conditions and positive result for Tollens Reagent

Answer 9

Warm sample with Tollens

Silver mirror forms + Coats Test Tube
Due to Ag+ to Ag

Tollens reagent is Ammonical Silver Nitrate

Question 10

Positive results for 2,4 DNPH

Answer 10

Yellow/Orange precipitate forms

Question 11

What reagent is used to reduce Aldehydes + Ketones back to Alcohols

Answer 11

LiAlH4
Provides hydride ( H-) ions

Question 12

Reagents + Conditions for carbonyl + Cyanide

Answer 12

HCN in KCN

HCN = H+ (+) CN-
Weak acid

HCN made in mix of KCN + H2SO4

Question 13

How do carbonyls react with cyanide

Answer 13

Nucleophilic addition

Question 14

What is produced as Bi-Product in the reaction of carbonyl + 2,4 DNPH

Answer 14

Water = it’s a condensation reaction

Question 15

What technique can be used to identify what Carbonyl is present in Unknown sample

Answer 15

Test with 2,4 DNPH to make sure it’s a carbonyl

Recrystallisation + testing melting point to compare with data book to identify

Question 16

Describe the Recrystallisation / Purifying of Carbonyl + 2,4 DNPH to identify Carbonyl

Answer 16

1- 2,4 DNPH + Carbonyl
2- Filter product with Hirsch funnel
3- Dissolve impure solid in warm ethanol
4- put in Ice bath
5- Filter product with Hirsch funnel again + rinse with ice cold water
6- let solvent evaporate = leaving dry crystals
7- put Crystals in capillary tube + measure melting point

Question 17

How is the impure solution filtered when using Hirsch or Büchner funnel

Answer 17

Filtered under suction

Question 18

What test can be used to test for a methyl carbonyl - in aldehyde or ketone

Answer 18

IodoForm reaction

Question 19

What does the IodoForm reaction do

Answer 19

Shortens carbon chain

Question 20

What colour precipitate is seen for a positive result of Iodoform reaction

Answer 20

Pale yellow precipitate

Question 21

Conditions for IodoForm reaction

Answer 21

Iodine in alkaline solution

= Warm sample with Iodine(I2) in potassium Iodide + aqueous potassium Hydroxide

Iodine
Potassium iodide
Potassium hydroxide

Question 22

Show the IodoForm reaction

Answer 22

Question 23

Prefix at end of aldehydes

Answer 23

-Anal

Question 24

Prefix at end of ketone

Answer 24

-Anone

Question 25

Name these 2 aldehydes + ketones

Answer 25

1 = methanal
2 = Ethanal
3 = Propanone
4 = 5-methyl Hexan-3-one