General Flashcards
What do carbonyl compounds contain?
Contain an acyl fragment R-C=O bonded to another group
What are the name endings of an aldehyde?
And general formula?
R-CO-H al
What are the name endings of an ketone?
And general formula?
R-CO-R one
What are the name endings of an carboxylic acid?
And general formula?
R-CO-OH
Oic acid
What are the name endings of an acyl chloride?
And general formula?
R-CO-Cl
Oyl chloride
What are the name endings of an acid anhydride?
And general formula?
R-CO-OCOR
oic anhydride
What are the name endings of an ester?
And general formula?
R-CO-OR
oate
What are the name endings of an amide?
And general formula?
R-CO-NH2
amide
What is a symmetrical anhydride?
This is when both R groups are the same
Describe the formula of a primary, secondary and tertiary amide
RCONH2 primary
RCONHR secondary
RCONR2 tertiary
What is a lactam?
This is a cyclic amide
What is a lactone?
A cyclic ester
How do you name carbonyls?
The carbonyl carbon has the lowest number
Number from the carbonyl carbon
The ester has the higher priority (the prefix oxo is used for C=O)
Describe the nature of the C=O bond
The carbonyl carbon is sp2 hybridised
Carbonyl group is planar and has bond angles of 120
Short and strong bond
Bond is polarised as the oxygen is more electronegative than the carbon
Why is the C=O bond react despite is being very short and strong?
The bond has polarity so it is still reactive
Describe a nucleophile attack of the C=O bond
1) the nucleophile attacks from either face of the planar C=O bond at an angle of 107
2) addition of nucleophile is energetically favourable because a strong sigma bond is formed at the expense of a weaker bond
3) workup at the end of the reaction
What do nucleophiles attack?
Nucleophiles attack the partially positive carbon atom in the C=O bond
What do electrophiles attack?
Electrophiles attack the partially negative oxygen atom in the C=O bond
Why are alpha carbons relatively acidic?
The -I and -M effect of the C=O bond explains why the hydrogen atom on the alpha carbon are acidic
What happens when an aldehyde or ketone reacts with a charged nucleophile in an addition
Intermediate alkoxide ion is formed
See mechanism
What happens when an aldehyde or ketone reacts with an uncharged nucleophile in an addition
The reaction can be catalysed by an acid
Double attack from neutral nucleophile
Double intermolecular proton transfer
The protonated acid acts as a nucleophile
See mechanism
What happens when an carboxylic acid reacts with a charged nucleophile in an substitution
Unstable alkoxide ion- tetrahedral intermediate
The halide is the leaving group
(See mechanism)
What happens when an carboxylic acid reacts with a uncharged nucleophile in an substitution
Neutral nucleophile attacks and then base
Unstable alkoxide ion
Halide leaving group
See mechanism
What is an alpha substitution reaction?
Involves a reaction of the position next to the C=O bond in, an aldehyde, ketone, ester
An intermediate enol or enolate ion acts as an nucleophile which reacts with an electrophile
See mechanism
What is a carbonyl- carbonyl condensation reaction?
Involves reactions of two carbonyl compounds to form a product with an new carbon carbon bond
What is an adol condensation reaction?
One of them undergoes an alpha substitution and the other undergoes a nucleophilic addition reaction
A water is eliminated from reaction- condensation reaction
See mechanism
What is an claisen condensation reaction?
When two carboxylic acid derivatives react, one of them undergoes an alpha substitution and the other undergoes a nucleophillic acyl substitution reaction
ROH is eliminated - condensation
See mechanism
Why are aldehydes more reactive than ketones?
On steric grounds- the nucleophile can approach aldehydes more readily and the resultant transition state is less crowded and lower in energy
On electronic grounds- the carbon atom of the C=O bond of a ketone is less electrophilic (less positive)- due to +I methyl groups
What is normally used to increase the rate of reaction with a neutral nucleophile?
An acid catalyst is often used
