Chem 1307 Ch 18.6 Hydrolysis of Amides
Summary
TLDRThis lesson explores the hydrolysis of amides, a reverse reaction to amidation, where water breaks down amide bonds. Using either acid or base catalysts and heat, amides can be hydrolyzed to form carboxylic acids and ammonium salts or carboxylate salts and amines, respectively. The process involves balancing chemical equations and understanding the role of water and catalysts in the reaction.
Takeaways
- π§ͺ Hydrolysis of amides involves breaking the amide bond using water, which is a reverse reaction of the amidation process.
- π₯ Hydrolysis reactions often require heat and a catalyst to proceed efficiently.
- π Base hydrolysis of amides results in the formation of a carboxylate salt and an amine, whereas acid hydrolysis yields a carboxylic acid and an ammonium salt.
- π The hydrolysis process involves the splitting of the amide bond between the carbonyl carbon and the nitrogen atom.
- π§ In acid hydrolysis, water molecules combine with HCl to form the carboxylic acid and the ammonium salt.
- π Base hydrolysis uses a base like sodium hydroxide to facilitate the reaction, leading to the formation of a carboxylate salt and an amine.
- π The goal of the lesson is to understand and write balanced chemical equations for the hydrolysis of amides.
- π Amines are weak bases and are soluble in water up to six carbons in length, after which solubility decreases due to increased nonpolarity.
- π¬ Amines can be classified as primary, secondary, or tertiary based on the number of alkyl groups attached to the nitrogen atom.
- 𧬠Amines can also be heterocyclic, with nitrogen atoms within a carbon ring, and can function as neurotransmitters.
- π Amines react with carboxylic acids to form amides, which can then be hydrolyzed to break them down.
Q & A
What is hydrolysis in the context of amides?
-Hydrolysis in the context of amides refers to the process of breaking an amide bond by adding water. It is a reverse reaction of amidation, where water and an acid or a base split the amide, often requiring a catalyst and heat to proceed.
What are the products of acid hydrolysis of an amide?
-In acid hydrolysis of an amide, the products are a carboxylic acid and an ammonium salt. The amide bond is broken, and water and acid interact with the nitrogen to form the ammonium salt.
What are the products of base hydrolysis of an amide?
-In base hydrolysis of an amide, the products are a carboxylate salt and an amine. The amide bond is broken, and the base reacts with the carbonyl carbon to form the carboxylate salt, while the nitrogen forms an amine.
Why is heat necessary in the hydrolysis of amides?
-Heat is necessary in the hydrolysis of amides to increase the rate of the reaction. It provides the energy needed for the molecules to overcome the activation energy barrier, making the reaction proceed faster.
What is the role of a catalyst in the hydrolysis of amides?
-A catalyst in the hydrolysis of amides helps to lower the activation energy of the reaction, thereby increasing the rate at which the amide bond is broken and the reaction proceeds.
How does the structure of an amide affect its hydrolysis?
-The structure of an amide, particularly the nature of the R groups and the length of the carbon chain, can affect the ease of hydrolysis. Longer chains and more complex structures may require more energy or different conditions for hydrolysis to occur.
What is the difference between the hydrolysis of an amide using an acid versus a base?
-The hydrolysis of an amide using an acid results in the formation of a carboxylic acid and an ammonium salt, whereas hydrolysis using a base results in the formation of a carboxylate salt and an amine. The choice of acid or base determines the nature of the products formed.
What is the chemical equation for the acid hydrolysis of n-methylpentanamide?
-The chemical equation for the acid hydrolysis of n-methylpentanamide involves the reaction of n-methylpentanamide with water and hydrochloric acid to produce ammonium chloride and pentanoic acid.
What is the chemical equation for the base hydrolysis of n-methylpentanamide?
-The chemical equation for the base hydrolysis of n-methylpentanamide involves the reaction of n-methylpentanamide with sodium hydroxide and water to produce sodium pentanoate and methylamine.
How do amines react with carboxylic acids to form amides?
-Amines react with carboxylic acids through a condensation reaction where the amine donates a hydrogen and the carboxylic acid donates a hydroxyl group, forming an amide and releasing a molecule of water.
What is the significance of the hydrolysis of amides in biological systems?
-In biological systems, the hydrolysis of amides is significant as it is involved in the breakdown of proteins and peptides. This process is crucial for the metabolism and recycling of amino acids in the body.
Outlines
π§ͺ Hydrolysis of Amides: Breaking Bonds with Water
This paragraph delves into the chemical process of hydrolysis as it pertains to amides. It explains that hydrolysis is essentially the reverse of amidation, where water is used to break down the amide bond. The process requires heat and possibly a catalyst to facilitate the reaction. The paragraph provides an example using n-methylpentanamide, illustrating how a base can cleave the amide bond to yield a carboxylate anion and an amine. It also contrasts this with acid hydrolysis, which results in a carboxylic acid and an ammonium salt. The goal is set to write balanced chemical equations for these hydrolysis reactions.
π Base and Acid Hydrolysis of Amides: A Comparative Analysis
The second paragraph continues the discussion on amide hydrolysis, focusing on the differences between base and acid hydrolysis. It describes the process of acid hydrolysis, where an amide reacts with acid and heat to form a carboxylic acid and an ammonium salt. The paragraph uses a step-by-step approach to show the chemical changes, emphasizing the role of water molecules in the reaction. It then contrasts this with base hydrolysis, where the products are a carboxylate salt and an amine. The paragraph also includes a practical example, detailing the hydrolysis of n-methylpentanamide with sodium hydroxide, and explains how to write the IUPAC names for the resulting products.
π Chapter Summary: Amines and Amides
The final paragraph serves as a comprehensive summary of the chapter on amines and amides. It starts by defining amines and their properties, such as their solubility in water and their weak basic nature. It also touches on the concept of heterocyclic amines and their role as neurotransmitters. The paragraph then connects amines to amides, explaining how they can react with carboxylic acids to form amides, which can later be hydrolyzed under either acidic or basic conditions. The summary concludes with a concept map that encapsulates the key points and reactions discussed throughout the chapter.
Mindmap
Keywords
π‘Hydrolysis
π‘Amides
π‘Acid Hydrolysis
π‘Base Hydrolysis
π‘Carboxylic Acid
π‘Carboxylate Salt
π‘Amine
π‘Ammonium Salt
π‘Condensation Reaction
π‘Catalyst
π‘Heat
Highlights
Hydrolysis of amides is a reverse reaction of amidation, involving the use of water to break the amide bond.
A catalyst and heat may be required for hydrolysis to proceed efficiently.
Base hydrolysis of an amide results in the formation of a carboxylate anion salt and an amine.
Acid hydrolysis of an amide leads to the production of a carboxylic acid and an ammonium salt.
The process of hydrolysis involves the splitting of the amide bond between the carbonyl carbon and the nitrogen.
In acid hydrolysis, water and hydrochloric acid are used to facilitate the reaction.
Ammonium salts are formed when hydrogens from water and hydrochloric acid bond with the nitrogen of the amide.
Base hydrolysis involves the reaction of the amide with a base like sodium hydroxide, resulting in a carboxylate salt and an amine.
The carboxylate salt and amine are the products of base hydrolysis, differing from the products of acid hydrolysis.
Sodium oxide from sodium hydroxide bonds with the carbonyl carbon to form a carboxylate salt in base hydrolysis.
Methylamine is an example of an amine product from the base hydrolysis of an amide.
Ammonium chloride is an example of an ammonium salt produced during acid hydrolysis.
The hydrolysis of amides can be represented by balanced chemical equations.
Hydrolysis reactions are more complex than initially described, involving the participation of water molecules.
Amine classification includes primary, secondary, and tertiary amines based on the number of alkyl chains bonded to nitrogen.
Amines are soluble in water up to six carbons in length, with solubility decreasing as the molecule becomes more nonpolar.
Amines react as weak bases in water with low Kb values, participating in neutralization reactions with acids.
Heterocyclic amines have a nitrogen atom within the carbon ring and can act as neurotransmitters.
Amines can react with carboxylic acids to form amides, which can later be hydrolyzed.
The chapter concludes with a concept map summarizing the topics of amines and amides, including their properties and reactions.
Transcripts
the next lesson will be 18.6 and it
describes the hydrolysis of amides so
just like we did a dehydration or a
condensation reaction to create the
amide we can also break them apart by
adding water hydrolysis means that we
are breaking a molecule apart with the
use of water
so this is a reverse reaction of the
amidation
and hydrolysis occurs when water and an
acid or a base split the amide so you
may need a catalyst to help this
reaction proceed you will also need heat
so that this reaction can go a little
faster
so here we have an example of an amide
you have n
methyl
pentanamide one two three four five
carbons in the chain with our amide here
and what we're gonna do is we're gonna
use the base to kind of get in between
this amide so we're going to break the
amide bond so what you're going to get
is the salt of the carboxylate anion if
you use a base
if you use an acid you're going to get
the carboxylic acid and of course on the
other end you're going to get the amine
or ammonia depending on what you have as
your side chains do we have hydrogens or
r groups
the goal of this section will be to
write balanced chemical equations for
the hydrolysis of amides
so we took a look at the base hydrolysis
we'll describe that in detail in just a
second but let's start with the amides
that undergo acid hydrolysis
so we're going to add acid and heat to
produce a carboxylic acid and an
ammonium salt
so earlier we said that this type of
reaction is going to break the amide
bond between the carbon of the carbonyl
and the nitrogen of the amide
so we're going to add water to help us
break that apart so part of the water is
going to go here to create the
carboxylic acid so oh and then the other
part of the water the hydrogen is going
to come with the chloride
and interact with the amine part right
with the nitrogen section to create a
quaternary ammonium salt so we're going
to add the two hydrogens one from the
water one from the hcl and that creates
nh4 plus and of course the counter ion
is the chloride from here so we had a
positive one
for our
hydrogen and a negative one for the
chloride so adding four hydrogens to the
nitrogen gives it a positive charge we
have the ammonium salt and of course the
counter ion is the chloride our product
is ammonium chloride and ethanoic acid
which is also known as acetic acid
so we did acid hydrolysis again you want
to see where that water is kind of going
to go on to this molecule you have a
portion of the water molecule
that's going to come onto the carbonyl
split this in half and then the hydrogen
along with this proton from the acid
are going to come on the nitrogen side
to create the ammonium salt because now
there's four hydrogens it's a positive
charge and the chloride is going to want
to interact with that ammonium because
we have a counter ion right opposites
attract
so this is the acid hydrolysis of a
mites
now let's take a look at the base
hydrolysis of a mite the reaction is
pretty similar in that you're going to
split
the amide between the carbon of the
carbonyl and the nitrogen of the amide
so you're going to break the amide bond
however what you get as a product is a
little bit different in this case you're
going to get the carboxylate salt and an
amine in our previous example the acid
hydrolysis gave us on a quaternary
ammonium salt and the carboxylic acid
where now we have the carboxylate salt
and the amine so what's going to happen
is you're going to have this sodium
and oxygen
come here
and the hydrogen come there
so this hydrogen is here now
and of course you have your carboxylate
now this is the simplest way to describe
this reaction and from this chemical
reaction it seems like the water itself
is not really being used but it is this
is a hydrolysis reaction this reaction
is a little bit more complicated than
what you're seeing but what i do want
you to know is that the sodium oxide is
going to come to make the carboxylate
salt and the hydrogen is going to come
to make the
amine so we're going to kind of simplify
it just a little bit in this reaction we
had n n-methylpropanamide
so there's my n-methyl one two three
propane amide reacting with sodium
hydroxide in the presence of heat to
create
sodium propanoate the propanoate is the
salt the sodium is the counter ion and
the amine is methylamine so let's try a
base hydrolysis of anamide this problem
asks us to draw the condensed structural
formulas and write the iupac names for
the products from the hydrolysis of
n-methylpentanamide with sodium
hydroxide so what is our given we have
our amide and methylpentanoid and we
have our base sodium hydroxide because
we have a base present then we know that
this is the base hydrolysis of an amide
and because we have a base hydrolysis
we know that we need to form a
carboxylate salt and an amine
let's try it
so here i've gone ahead and drawn the
amide we have n methylpentanomide
here's my n methyl one two three four
five carbons
in my amide so end methylpentanomide
reacting with sodium hydroxide now i
colored in the sodium oxide part of
sodium hydroxide blue so you could see
where that's going to go and the
hydrogen red so also we can pinpoint
where that's going to go
so let's go ahead and split up our
molecule in half here at the amide bond
right and we said that this portion the
sodium oxide is going to go with the
carbon of the carbonyl
and the hydrogen is going to go with the
nitrogen
to create the amine
the sodium oxide creates the carboxylate
salt so let's go ahead and draw our
products
so what we're going to get is
ch
ch2 ch2
ch2 that's 4
c double bond o
and then
we have our
o minus
n a
plus
this is our
carboxylate
salt
okay
so the sodium hydro sodium oxide bonded
to the carbon of the carbonyl now what's
my other product so my other product is
the amine
so i had n
ch3
h and now we have that hydrogen from the
base
so this gives me my amine
this compound here the carboxylate salt
is called sodium we have sodium
pentanoate
is the carboxylate salt and the amine is
methyl amine if you use the common name
which is
often used
or
methanoid
excuse me methanamine
if you're using iupacne
so these are our products
so let's check our solution we did get
sodium pentanoate as our carboxylate
salt and methanamine as our amine
so let's try this learning check
draw the condensed structural formulas
for the products from the hydrolysis of
the following amide with hcl so this
particular one is an acid hydrolysis
we're going to use water and acid
all right so this is an acid hydrolysis
we have n methylpropanamide
so n methyl one two three propane amide
reacting with water and hydrochloric
acid to produce
we know we need to get the carboxylic
acid right so we're gonna get a
carboxylic acid
plus an ammonium
salt okay so let's create
those two compounds
first we want to show where we're going
to break the molecule we're going to
break the amide bond that's the bond
between the carbon of the carbonyl and
the nitrogen of the amide i've colored
the different
atoms and the molecules that are
reacting with the amide um
sort of color coordinated so we can see
where those
different portions of the molecule are
going
um so for one we're going to create our
carboxylic acid right so
this particular region of the water
is going to
[Music]
bond
to
the carbonyl right the carbon of the
carbonyl that's going to create our
carboxylic acid then we're going to have
these hydrogens
interacting or bonding to the nitrogen
to create the ammonium ion and the
counter ion the chloride will bond
electrostatically to that ammonium ion
to create the ammonium salt so let's do
the first part we have our carboxylic
acid so let's draw it ch3
ch2
carbonyl oh this is one two three this
is
propanoic
acid
right and of course we probably want to
highlight this blue so we can show that
that came from the water
then we have our
ammonium ion
so n we had an r group which was a ch3
we had an a hydrogen
and now from the water comes one
hydrogen from the hcl comes another
hydrogen creating a positively charged
ammonium ion
and that is attracted to the counter ion
the chloride so what we have as our
product here is n
methyl
ammonium
chloride
and those are our two products for the
acid hydrolysis of this amide
so let's check our answer
we did get propanoic acid right and then
we got the
n methyl ammonium chloride they didn't
add in the counter ion here but i'm
going to go ahead and add in that
chloride because remember we said this
is an ammonium
salt in order to have the salt you need
both the plus and the minus
so this concludes our lesson on the
hydrolysis of amides this also concludes
the chapter 18 topics amines and amides
so here we have the concept map that
kind of summarizes what we learned in
this chapter
make sure that you do include this in
your notes because it is really helpful
so we have a means and a minds let's
start with the amines amines have a
nitrogen atom they are bonded to an
alkyl chain or an aromatic group and of
course it can be bonded to more than one
alkyl chain we did our classification of
primary secondary and tertiary amines
they are soluble in water up to six
carbons long right after five carbons
they start to struggle because the
molecule becomes more nonpolar
these react in water as a weak bases and
they're very weakly basic so they have
low kbs
and they're going to react with acids in
a neutralization reaction
amines can also be heterocyclic which
means that there's a nitrogen within the
carbon chain right within the carbon
ring
these amines can also act as
neurotransmitters neurotransmitters are
substances that create the nerve
impulses amines can react with
carboxylic acids to form amides
then amides can be broken down in a
hydrolysis reaction
to form either carboxylic acids and
ammonium salts or carboxylate salts and
amines depending on whether you use acid
hydrolysis or base hydrolysis
so this kind of summarizes what we
learned in this chapter
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