100% satisfaction guarantee Immediately available after payment Both online and in PDF No strings attached
logo-home
Chemical properties of Aldehydes and Ketones $17.99   Add to cart

Exam (elaborations)

Chemical properties of Aldehydes and Ketones

 6 views  0 purchase
  • Course
  • Chemical properties of Aldehydes and Ketones React
  • Institution
  • Chemical Properties Of Aldehydes And Ketones React

Chemical properties of Aldehydes and Ketones Reactions common to both Aldehydes and Ketones The difference between an Aldehyde and a Ketone is the position of the C=O (Carbonyl group). Aldehyde – always on a carbon at the end of the chain Ketone – Always on a carbon at middle carbon of the ...

[Show more]

Preview 4 out of 45  pages

  • February 15, 2024
  • 45
  • 2023/2024
  • Exam (elaborations)
  • Questions & answers
  • Chemical properties of Aldehydes and Ketones React
  • Chemical properties of Aldehydes and Ketones React
avatar-seller
laurenjames
Chemical properties of Aldehydes and Ketones

Reactions common to both Aldehydes and Ketones

The difference between an Aldehyde and a Ketone is the position of the C=O (Carbonyl group).

Aldehyde – always on a carbon at the end of the chain
Ketone – Always on a carbon at middle carbon of the chain

1. BOTH Aldehydes and Ketones can be reduced

Aldehyde reduced to Primary Alcohol
Reducing agent = Sodium tetrahydroborate III (NaBH4)
Ketone reduced to Secondary Alcohol

Reduction Oxidisation
Gain of Electrons Loss of Electrons

H
O

H3C C
+ 2[H]  H3C C OH

H H

True for all secondary alcohols
Carbonyl + 2[H] ─(NaBH4) Alcohol

CH3CH2CHO + 2[H]  CH3CH2CH2OH
Propanal + NaBH4  Propan-1-ol

CH3COCH3 +2[H]  CH3CH(OH)CH3
Propanone + NaBH4  Propan-2-ol

2. BOTH Aldehydes and Ketones undergo nucleophilic substitution using HCN

Def.
A nuclophile is an electron pair donor

E.g. NH3 – 1 lone pair
H2O – 2 lone pairs
OH– – 3 lone pairs
Cl– – 4 lone pairs
Therefore nucleophiles attack
E.g. Cδ+=Oδ– 1
Due to a difference in electronegativity the O is
electronegative than the C so attracts the electron
pair more strongly

, NOTE:

C C – A C=C will undergo
C C = electrophillic addition
reactions and the reagents
are added across the double
bond



– A C=O double bond
undergo nucleophillic
addition reactions and the
C reagents are added across
C O = O
the double bond




Mechanism of the reaction between Ethanal and HCN

Conditions: K+CN– = catalyst
Reagents: O
+ HCN(g)
H3C C H


δ+ O δ+ δ–
H3C C H CN
O H
H
Ethanal  Intermediate  HC C H
O 3
2 Hydroxylpropanenitrile
N C C CN
H3C H
KCN Nitrile group
CN


Mechanism of the reaction between Propanone and HCN
δ+ δ–
H CN
Conditions: K+CN– = catalyst
Reagents: O
O O H
2
H3C C CH3 HC C CH HC C CH
3 3 3 3
Propanone  
CN CN
N C 2 Hydroxyl 2 methylpropanenitrile
Intermediate
KCN

, 3. BOTH react with 2,4, Dinitrophenylhydrazine (2,4, DNPH)

 2,4,DNPH is an orange solution
 The reaction is used as a test for the C=O double bond
 Reacts to give an orange/yellow precipitate


H3C

H2N C N + H2O
HC C O
3
NH H NH
O O
H
Ethanal + +
 +
N N

+ O + O
O N O N Orange/Yellow
2,4, DNPH precipitate
O O



Example exam Q.
Q. How can you distinguish between an Aldehyd and a Ketone? (4 marks)

A.  Dissolve in 2,4 DNPH if precipitate is found the C=O bond present
 Orange precipitate is purified by recrystalisation
 Dry the crystals and heat them until their melting point is found
 check the melting point found against data
 Identify the exact Aldehyde or Ketone found


Reactions for Aldeydes only

1. ONLY Aldeydes can be oxidised with Acidified Dichromate (H+/Cr2O 72-)


Primary Alcohol  Aldehyde  Carboxylic Acid

Secondary Alcohol  Ketone

Tertiary Alcohol


O H O
H3C C + [O]  H C C
3
H H OH
H+/Cr2O72-
Ethanal Acidified Dichromate Ethanoic Acid

, 2. ONLY Aldehydes can react in the Silver mirror test (Tollens Test)

Reagents: Silver nitrate dissolved in Amonnia (Ag+ (NH 3)2 )
Conditions: Hot water bath

 If an Aldehyde is present the Silver ion (Ag+) changes to a silver atom (Ag)

Ag+ + 1e–  Ag(s)
ion – 46e– atom – 47e–

 As the Aldehyde was oxidised the Ag+ gained an electron and was reduced
 Aldehydes Carboxylic Acid KetonesNo further reaction




4

The benefits of buying summaries with Stuvia:

Guaranteed quality through customer reviews

Guaranteed quality through customer reviews

Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.

Quick and easy check-out

Quick and easy check-out

You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.

Focus on what matters

Focus on what matters

Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!

Frequently asked questions

What do I get when I buy this document?

You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.

Satisfaction guarantee: how does it work?

Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.

Who am I buying these notes from?

Stuvia is a marketplace, so you are not buying this document from us, but from seller laurenjames. Stuvia facilitates payment to the seller.

Will I be stuck with a subscription?

No, you only buy these notes for $17.99. You're not tied to anything after your purchase.

Can Stuvia be trusted?

4.6 stars on Google & Trustpilot (+1000 reviews)

66579 documents were sold in the last 30 days

Founded in 2010, the go-to place to buy study notes for 14 years now

Start selling
$17.99
  • (0)
  Add to cart