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Naming acyl chlorides
Name the acyl group and add the word chloride. When
naming the acyl group, replace the ic acid ending of the
IUPAC name of the corresponding carboxylic acid by yl. If R is
a ring other than benzene, the suffix carbonyl chloride is
used after the full name of the ring.
TERM 2
Naming acid anhydrides
DEFINITION 2
When both acyl groups are the same, name the acid and
replace the ending acid with anhydride. When the groups are
different, list the names of the corresponding acids in
alphabetical order and replace the ending acid with the word
anhydride.
TERM 3
Naming esters
DEFINITION 3
The ester is named as alkyl alkanoates. Cite the alkyl group
attached to oxygen first (R'), then name the acyl group
second; substitute the suffix -ate for the -ic acid ending of the
corresponding acid.
TERM 4
Naming amides
DEFINITION 4
Identify the corresponding carboxylic acid, replace the -ic
acid or -oic acid ending with amide. For amides with
substituents on N, precede the name of the amide with the
name of the appropriate substituent(s) and place the letter N
(standing for nitrogen) before the substituent to indicate its
locant.
TERM 5
Naming
nitriles
DEFINITION 5
Add the suffix -nitrile to the name of the parent hydrocarbon
chain (including the triply bonded carbon of CN). or Replace
the -ic acid or -oic acid name of the corresponding carboxylic
acid with onitrile. or Name as an alkyl cyanide (functional
class name).
Structure and reactivity of carboxylic acid
derivatives
The main structural feature that distinguishes acyl chlorides, anhydrides, esters, and amides is the interaction of the substituent with the carbonyl group. It can be represented in resonance terms as: The extent to which the lone pair on X can be delocalized into C=O depends on: 1) The electronegativity of X 2) How well the lone pair orbital of X interacts with the orbital of C=O Acyl chlorides have the least stabilized carbonyl group. Delocalization of lone pair of Cl into C=O group is not effective because CCl bond is too long. Lone pair donation from oxygen stabilizes the carbonyl group of an acid anhydride and an ester. Stabilization in ester is greater than comparable stabilization of an anhydride. Lone pair donation from nitrogen stabilizes the carbonyl group of an amide. Because N is less electronegative than O, amides are stabilized more than esters and anhydrides. Due to the very efficient electron delocalization and dispersal of negative charge in carboxylate anion, carboxylate has the maximum stabilization. TERM 7
Nucleophilic acyl substitution reaction
DEFINITION 7 Reaction is feasible when a less stabilized carbonyl is converted to a more stabilized one (i.e. more reactive to less reactive). General reaction mechanism of nucleophilic acyl substitution involves formation and dissociation of a tetrahedral intermediate (TI). Formation of tetrahedral intermediate is analogous to nucleophilic addition to C=O of aldehydes and ketones. Elimination of TI restore C=O group. The TI can exist in neutral form, conjugated acid form or conjugate base form. TERM 8
Nucleophilic acyl substitution in acyl chlorides
DEFINITION 8 Acyl chlorides react with carboxylic acids to give acid anhydrides. Pyridine acts as catalyst and base. Acyl chlorides react with alcohols to give esters. Pyridine acts as catalyst and base. Acyl chlorides react with ammonia and amines(10 or 20) to give amides. Acyl chlorides react with water to givecarboxylic acids (carboxylate ion in base). TERM 9
Nucleophilic acyl substitution in acid
anhydrides
DEFINITION 9 Carboxylic acid anhydrides react with alcohols to give esters. Normally, symmetrical anhydrides are used (both R groups the same). Reaction can be carried out in presence of pyridine (a base) or it can be catalyzed by acids. Acid anhydrides react with ammonia and amines (10 or 20) to give amides. Acid anhydrides react with water to givecarboxylic acids (carboxylate ion in base). TERM 10
Physical properties of esters
DEFINITION 10
Esters have higher boiling points than alkanes because they
are more polar. Esters cannot form hydrogen bonds to other
ester molecules, so have lower boiling points than alcohols.
Esters can form hydrogen bonds to water, so low molecular
weight esters have significant solubility in water. Solubility
decreases with increasing number of carbons.
Reactions of esters with LiALH
Form 10 alcohol as the product. The OR group is also
converted to an alcohol ROH.
TERM 17
Physical properties of amides
DEFINITION 17
Amides (R= H or alkyl) can form intermolecular hydrogen
bonds with each other, thus they have higher boiling points
than corresponding carboxylic acids. Amides are less acidic
than carboxylic acids (because N is less electronegative than
O), but more acidic than amines (C=O is an EWG).
TERM 18
Preparation of amides
DEFINITION 18 Reaction of acyl chlorides, anhydrides or esters with NH3, RNH2 or R2NH When using acyl chlorides or anhydrides, 2 eq. of amines are required. One eq. of amines act as nucleophile, another eq. act as base to neutralize the generated acids. Carboxylic acids react with amines to get ammonium carboxylate salt (acid-base reaction). Heating the salt convert it to an amide. TERM 19
Hydrolysis of amides
DEFINITION 19 Hydrolysis can be done in acidic or basic solutions. In acidic solution, a carboxylic acid and an ammonium salt are generated as products. Reaction mechanism: Protonation of the C=O oxygen to activate the C=O carbon; addition of H2O to form tetrahedral intermediate; breakdown of the TI by elimination of an amine; the formed amine is protonated to become ammonium salt. In basic solution, a carboxylate salt and amine are obtained as the products. Reaction mechanism: -OH is added to the C=O group to form the TI; breakdown of the TI gives carboxylic acid and amine; carboxylic acid is deprotonated to get carboxylate salt. TERM 20
Preparation of
nitriles
DEFINITION 20
Nucleophilic substitution by cyanide onalkyl halides (SN2)
Alkyl halides must be methyl, 10 or 20 halides. 30 halides
undergo elimination reaction; aryl and vinyl halides do not
react. Cyanohydrin formation from ketones or aldehydes
Dehydration of amides
Reactions of
nitriles
Hydrolysis of nitriles Hydrolysis can be carried out in acidic or basic solutions. Acid hydrolysis yields a carboxylic acid and an ammonium ion. Basic hydrolysis yields a carboxylate ion and ammonia. Reaction of nitriles with Grignard reagents Nucleophilic addition of R- on CN yields an imine; imine is hydrolyzed to give a ketone as the product.
