Transcript aldehydes powerpoint

Aldehydes
By: Nicole Murphy & Michaela Miller
General Structure
• What makes an aldehyde an
aldehyde? A carbon double
bonded to an oxygen
molecule. This is called a
carbonyl group. Bonded to
this carbonyl group is a
hydrogen molecule.
General structural formula
Naming
Aldehydes are named using the IUPAC rules.
• 1) Identify the longest carbon chain
with the carbonyl group.
Naming cont.
2) When numbering, the carbonyl
group is always number 1.
3) Identify the branched
attachments (alphabetically) and
prefix the carbon number it is
attached to. If there is more
than one of the same type use
prefixes. Ex: di for 2, tri for 3
ect.
Naming cont.
4) Use the alkane name
that represents the number
of carbons in the longest
chain.
5) Change the “e” ending
and replace it with “al”.
Try this….
Answer….
• 2-methylpropanal
Try this…
•Draw:
- Hexanal
Answer
Everyday use:
•Hexanal is actually used in
the flavour industry to
produce fruity flavours,
although its scent resembles
that of freshly cut grass.
• Smaller Aldehydes have a
stronger, sharp, pungent odour.
Larger Aldehydes have an almost
rosy smell, or a sweet smell.
• Formaldehyde (or CH2O) can be used to preserve
dead animals.
• Acetone is commonly found in fingernail polish
remover and is a solvent.
• 2-Butanone is used as a solvent and paint stripper.
•Aldehydes are famously
produced as ingredients in
perfumes and flavors.
• Carvone is used as spearmint flavoring.
• Vanillin is the vanilla flavoring and gives vanilla
beans their aroma. (Often appears in nature)
• Cinnamaldehyde smells like cinnamon.
Properties of Aldehydes
• Aldehydes have a higher boiling point than
Alkanes of similar size and structure.
• Ex. Boiling point of 2-methylpropanal :
63˚C vs. Boiling point of 2methylpropane: 11.7 ˚C
• Aldehydes with lower molecular weight
have high water solubility (ex.
Formaldehyde).
Common reactions
• Aldehydes are formed by partial oxidation of
primary alcohols and form carboxylic acids when
they are further oxidized.
• Two common aldehyde reactions are either the
reduction or oxidation reaction. When an oxidizing
agent is added to a primary alcohol it forms an
aldehyde, or if an aldehyde is reduced, it can form
a primary alcohol.
REACTION
Synthesis:
A primary alcohol reacts with an oxidizing agent to make
an aldehyde
R-OH + Ox.Agent  RH= O
Example:
1-Propanol is oxidized to propanal
CH3CH2CH2OH + Ox.Agent  CH3CH2CHO
Examples of Oxidizing Agents
An oxidizing agent is the substance that
provides oxygen or removes hydrogen
from another substance.
• Permanganate (MnO4-)
• When Hydrogen gas reacts with metals it is
an oxidizing agent. (H2(g))
• Oxygen gas (O2 )
Another Oxidation Reaction
• Tollens' reagent is a chemical reagent most
commonly used to determine whether a known
carbonyl-containing compound is an aldehyde or a
ketone. It is usually ammoniacal silver nitrate, but
can also be other mixtures, as long as aqueous
diamminesilver(I) complex is present. It was
named after its discoverer, Bernhard Tollens.
• A positive test with Tollens' reagent results in
elemental silver precipitating out of solution,
occasionally onto the inner surface of the reaction
vessel, producing a characteristic and memorable
"silver mirror" on the inner vessel surface.