aldehydes and ketones i nucleophilic addition to carbonyl n.
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ALDEHYDES AND KETONES I. NUCLEOPHILIC ADDITION TO CARBONYL. Chapter 16. Reading Assignment. DO: Sections 16.0 through 16.7 SKIP: Section 16.8 DO: 16.9 through 16.18 SKIP: Section 16.19 DO: Section 16.20 Organic Nomenclature: Aldehydes and Ketones. Problem Assignment.

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reading assignment
Reading Assignment
  • DO: Sections 16.0 through 16.7
  • SKIP: Section 16.8
  • DO: 16.9 through 16.18
  • SKIP: Section 16.19
  • DO: Section 16.20
  • Organic Nomenclature: Aldehydes and Ketones

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problem assignment
Problem Assignment
  • In-Text Problems
    • 16.1 through 16.27
  • End-of-Chapter
    • 1 through 6
    • 7a; 7c through 7j
    • 8 b, c, d
    • 9 through 10
    • 12 through 14

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slide4

Aldehyde

Ketone

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iupac nomenclature of ketones
IUPAC Nomenclature of Ketones
  • Choose the longest continuous carbon chain that contains the carbonyl carbon
  • Number from the end of the chain closest to the carbonyl carbon
  • Ending is -one
  • Do the ketonessection of Organic Nomenclature -- Assignment!

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example
Example

2-Pentanone

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another
Another...

4-Ethyl-3-hexanone

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and another
And another...

3-Isopropylcyclopentanone

or 3-(1-Methylethyl)cyclopentanone

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common or trivial names
Common, or Trivial, Names
  • Name each group attached to the carbonyl group as an alkyl group
  • Combine into a name, according to:
    • alkyl alkyl’ ketone
  • NOTE: This is not all one word!

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example of a common name
Example of a Common Name

Methyl propyl ketone

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another example
Another example...

Diethyl ketone

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important example
Important example!

Dimethyl ketone

Acetone

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another important common name
Another Important Common Name

Acetophenone

(Methyl phenyl ketone)

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iupac nomenclature of aldehydes
IUPAC Nomenclature of Aldehydes
  • Choose the longest continuous carbon chain that contains the carbonyl carbon
  • Number from the end of the chain closest to the carbonyl carbon (this will automatically be carbon #1!)
  • Ending is -al
  • Note: The carbonyl carbon is not identified by number in the final name.
  • Do the aldehydessection of Organic Nomenclature -- Assignment!

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example1
Example

Hexanal

Notice that there is no “-1-” in the name!

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another1
… another:

5-Methylhexanal

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one more
One more:

3-Phenylpropanal

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for cyclic molecules the ending is carbaldehyde
For cyclic molecules, the ending is -carbaldehyde

Cycloheptanecarbaldehyde

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two acceptable alternative names
Two acceptable alternative names:

Benzenecarbaldehyde (official IUPAC name)

Benzaldehyde (acceptable IUPAC name)

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also iso names
Also: “Iso” names:
  • Whenever there is a -CH(CH3)2 group, an alternative common name is an “iso” name.
  • The “iso” name includes all of the carbon atoms in the molecule.
  • The “iso” name isn’t used if there are other substituents.

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example2
Example

b-Methylbutyraldehyde

Isovaleraldehyde

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another example1
Another example...

e-Bromocaproaldehyde

w-Bromocaproaldehyde

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benzaldehyde
Benzaldehyde

ortho (o-) meta (m-) para (p-)

1,2- 1,3- 1,4-

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more than one subsituent
More than one subsituent:

4-Hydroxybutanal

g-Hydroxybutyraldehyde

The prefix for -OH is hydroxy

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slide27
Also...

2-Methoxypentanal

a-Methoxyvaleraldehyde

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slide28

Bourgeonal is thought to be a chemoattractant emitted by the egg and detected by an odor receptor on the sperm cell. This guides the sperm to the egg

Science, 299, 2054 (2003)

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structure of the carbonyl group
Structure of the Carbonyl Group
  • Hybridization of the carbonyl carbon is sp2.
  • Geometry of the carbonyl carbon is trigonal planar
  • Attack by nucleophiles will occur with equal ease from either the top or the bottom of the carbonyl group.
  • Hybridization of the oxygen is “nominally” sp2.

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prochiral
Prochiral

The carbonyl carbon is prochiral. That is, the carbonyl carbon is not the center of chirality, but it becomes chiral as the reaction proceeds.

These two products are enantiomers.

In general, both enantiomers are formed in equal amount.

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reaction of the carbonyl group with acids
Reaction of the Carbonyl Group with Acids

Typical behavior

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reaction of the carbonyl group with bases
Reaction of the Carbonyl Group with Bases

Typical behavior

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nucleophilic addition to carbonyl general mechanism
Nucleophilic Addition to Carbonyl -- General Mechanism

NOTE: Reversible reaction

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nucleophilic addition to carbonyl in acid general mechanism
Nucleophilic Addition to Carbonyl -- in Acid (General Mechanism)

NOTE: Reversible reaction

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the carbocation intermediate has resonance
The carbocation intermediate has resonance.

The positive charge character on carbon makes this an excellent site for attack by Lewis bases (nucleophiles).

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once we have the intermediate what happens to it
Once we have the intermediate, what happens to it?

Case 1: The Addition Product is Stable.

The reaction stops here. This happens most often when the nucleophilic atom is carbon, oxygen, or sulfur.

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slide37

Case 2: Addition-Elimination

The addition product is unstable with respect to loss of a molecule of water. This is observed most often when the nucleophilic atom is nitrogen or phosphorus.

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slide38

Case 3: Loss of Leaving Group

This process is observed when X is a potential leaving group. In this case we have nucleophilic acyl substitution (see Chapter 19).

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what are the stereochemical requirements
What are the stereochemical requirements?
  • The hybridization of carbon in the carbonyl group issp2
  • The geometry around carbon is trigonal-planar.
  • Nucleophile can attack the carbonyl group equally easily from top or bottom (see model)
  • BUT: aldehydes react faster than ketones in nucleophilic addition!

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slide40
Why?
  • Aldehydes have a hydrogen attached to the carbonyl group, whereas ketones have an alkyl group.
    • Alkyl groups are much more bulky than hydrogens -- hence ketones should show some steric hindrance.
  • Alkyl groups have a small electron-releasing inductive effect.
    • This should make the carbonyl carbon less favorable by attack by nucleophile.
  • The answer is that there is a combination of steric hindrance and inductive effects that makes ketones react slower than aldehydes.

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addition of cyanide 16 6
Addition of Cyanide (16.6)

A cyanohydrin

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mechanism
Mechanism

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example3
Example
  • Notice that the cyanide ion and the acid are added in two separate steps!
  • Sodium carbonate is used to keep the reaction medium basic.

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so what s it good for
So, what’s it good for?

Nitriles can be hydrolyzed to form carboxylic acids.

This affords us with an important method of synthesizing a-hydroxy-carboxylic acids -- important intermediates in biochemical processes.

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reaction with organometallic compounds 16 7
Reaction with Organometallic Compounds (16.7)

The products of this sequence are always alcohols.

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addition of organometallic reagents
Addition of Organometallic Reagents

The products of the addition are always alcohols.

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slide48

Whatever is attached to the carbonyl group will be attached to the resulting alcohol carbon.

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example4
Example

Organometallics react with ketones to yield tertiary alcohols.

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and another1
And another...

Organometallics react with aldehydes to form secondary alcohols

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summary of reactions of organometallics with carbonyl compounds
Summary of Reactions of Organometallics with Carbonyl Compounds
  • Organometallics with ketones yield tertiary alcohols
  • Organometallics with aldehydes yield secondary alcohols
  • Organometallics with formaldehyde yield primary alcohols.

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ethynylation
Ethynylation

One can also use a Grignard reagent to do an ethynylation.

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to make an alkynyl grignard
To make an alkynyl Grignard...

This is an acid-base reaction (the proton is transferred from the stronger acid to the stronger base).

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a practical application
A Practical Application

Used in oral contraceptives

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