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O r g a n i c C h e m i s t r yO r g a n i c C h e m i s t r y
Dr.Dr. DikdikDikdik KurniaKurnia,, M.ScM.Sc
Carboxylic Acids and Their DerivativesCarboxylic Acids and Their Derivatives
LaboratoriumLaboratorium KimiaKimia OrganikOrganik JurusanJurusan KimiaKimia
FakultasFakultas MatematikanMatematikan dandan IlmuIlmu PengetahuanPengetahuan AlamAlam
UniversitasUniversitas PadjadjaranPadjadjaran
20092009
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Carboxylic Acids and Their Derivatives
1. What are the general properties of carboxylic acids and their derivatives?Be able to describe and compare such properties as hydrogen bonding,water solubility, boiling point, and acicidity or basicity.
2. How are carbocylc acid, anhydrides, esters, and amides named?Be able to name t he simple members of these families and write therstructures, given the names.
3. What are some of the significant applications and occurences of carbocylic
, , ,Be able to identify major applications and occurrences of each family ofcompoundsand describe some important members of each family.
4. How are esters and amide synthesized from carboxylic acids and convertedback to carboxylic acids?Be able to describe and predict the products of the ester- and amide-forming reactions of carbocylic acids and the hydrolysis of esters andamides.
5. What are phosphate esters and anhydrides, and why are they important?Be able to recognize and writ e the structures of phosphate esters andanhydrides and explain why they are important in biochemistry.
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Carboxylic Acids and Their Derivatives
Carbocylic acid (RCOOH):
A com ound that ha a carbon l rou bonded to on carbon substit uentand one OH group.
Acid anhydride(RCO2COR'):
A compound t hat has a carbonyl group bonded t o a carbon substit uent andan OCOR' group.
Ester (RCOOR'):
A compound t hat has a carbonyl group bonded to one carbon atom and one
ORgroup.Amide (RCONR'2):
A compound that has a carbonyl group bonded to one carbon atom andnitrogen atom group, where R' may be an H atom.
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Properties of Carboxylic Acids and Their Derivatives
Carbocylic acid, acid anhydrides, esters, and amides all have their carbonyl groups
bonded to an atom (O and N) that strongly attracts electrons.
The carbonyl groups are more strongly polarized in these families of compounds
than in ketones and aldehydes.
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Properties of Carboxylic Acids and Their Derivatives
The structural similarity of theses families also leads to similarities in their chemistry.
All undergo carbonyl-group substitution reactions, in which a group we can
represent as X replaces (substitutes for) OH, OCOR, OR, or NH2 group of
the starting material
Amides and esters can easily be either made from acids or converted back to acids.
Acid anhydrides are the most reactive of these carboxylic avid derivaives, and they
cannot be used in aqueous solution because of their substitution reaction withwater.
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Properties of Carboxylic Acids and Their Derivatives
Carbocylic acids and their derivatives all contain polar functional groups, all are
higher boiling point than comparable alkane.
Like alcohol, carbocylic acids can form hydrogen bonds witheach other.
Molecules pair off to form dimers, and even formic acid (HCOOH), the lighest and
simplest carrbocylic acid, is a liquid at room temperature with a boiling point of
101C.
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Properties of Carboxylic Acids and Their Derivatives
Acids with saturated straght-chain R groups contaning up to nine carbon atoms are
volatile liquids with stron, sharp odors, and those with up to four carbons are
water-soluble.
Higher saturated acids are waxy, odorless solids, and water solubility falls off as the
size of the alkane-like portion increases relative to the size of water-soluble
COOH portion.
When the OH of the carboxyl group (COOH) is converted to the OR of an ester,
the ability of the molecules to hydrogen-bond with each other is lost.
Simle esters are therefore lower boilin than the acids from which they are derived
and are also lower boiling than comparable alcohols.
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Properties of Carboxylic Acids and Their Derivatives
Replacement of the OH group of an acid by an NH2 group produces an
unsubstituted amide (RCONH2), that is, an amide with two hydrogen atoms on
the nitrogen atom.Such amide can form three strong hydrogen bonds to other amide molecules and are
thus higher melting and higher boiling than the acids from which they are
derived.
Note the distinction between amines and amides.
The nitrogen atom is bonded to a carbonyl-group carbon atom in an amide, but not
in an amine.
Amides are not basic like amines, mainly because the electron-withdrawing ability of
the carbonyl group causes the unshared pair of electrons on nitrogen to be held
tightly and prevents it from bonding to hydrogen.
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Properties of Carboxylic Acids and Their Derivatives
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Properties of Carboxylic Acids and Their Derivatives
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Properties of Carboxylic Acids and Their Derivatives
All undergo carbonyl-group substitution reactions
Acids anhydrides react with water to form acids Esters and amides are made from acids and easily converted back to acids
Hydrogen bonding is strong in pure acids and unsubstituted or monosubstituted
amides; none in esters.
Simpler acids and esters are liquis; all unsubstituted amides except formamide
are solids.
Acids give acidic aqueous solutions; esters and amides do not change pH.
Volatile acids have strong odors; volatile esters have pleasent, fruity odors.
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Naming of Carboxylic Acids and Their Derivatives
Carbocylic acids,
Carbocylic acids (RCOOH) are named systematically by replacing
the final eof the corresponding alkane name with oicacid. If alkyl substituents or other functional groups are present, the
chain is numbered beginning at the COOH end.
Dicarbocylic acids,
Dicarbocylic acids which contain two COOH groups are named systematically
by the ending dioic to the alkane name (the e is retained).
If alkyl substituents or other functional groups are present, the chain is
numbered beginning at the COOH end.
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Naming of Carboxylic Acids and Their Derivatives
Many other varieties of compounds containing COOH group are also common.
There are unsaturated acids, which are named systematically with the ending-enoic,
and there are acids containing other functional groups such as hydroxy acids and
keto acids, several of which are important biomolecules.
The carbon atoms next to the COOH group are sometimes identified by Greek
letters, beginning with .
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Naming of Carboxylic Acids and Their Derivatives
Acid Anhydrides,
The word anhydride means without water and acid anhydride have the
structure that results from lossof a molecule of water by two acid molecules(whether or not the anhydride is made that way).
Anhydride names are derived by replacing acid in the name of the original acid
with anhydride.
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Naming of Carboxylic Acids and Their Derivatives
Ester,
Ester (RCOOR') are named by first specifying the alkyl group attached to the
ether-like oxygen (OR') and then identyfing the related carbocylic acid The family name ending icacid is replaced by -ate.
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Ester names always consist of two wordsthe name of alkyl group in COOR
followed by the name of the acid with an ate ending.
Naming of Carboxylic Acids and Their Derivatives
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Amides (RCONH2),
Amides with an unsubstituted NH2 group are named by replacing the oic acid
of the corresponding carboxylic acid name with amide. If the nitrogen atom of the amide has alkyl substituents on it, the compound is
named by first specifying the alkyl group and then identfying the amide name.
The alkyl substituents are preceded by the letter N to identify them as being
attached directly to nitrogen.
Naming of Carboxylic Acids and Their Derivatives
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Naming of Carboxylic Acids and Their Derivatives
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Some Common Carboxylic Acids
Carboxylic acids occur widely throughout the plant and animal kingdoms.
Long-chain carboxylic acids such as stearic acid are components of all animal fats
and vegetable oil, and many organic acids are formed in the body during the
beakdown of foods.
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Some Common Carboxylic Acids
Acetic acid (CH3COOH)
Carboxylic acids occur widely throughout the plant and animal kingdoms.
Long-chain carboxylic acids such as stearic acid are components of all animal fatsand vegetable oil, and many organic acids are formed in the body during the
beakdown of foods.
Citric acid (A Tricarboxylic Hydroxy Acid)
Carboxylic acids occur widely throughout the plant and animal kingdoms.
Long-chain carboxylic acids such as stearic acid are components of all animal fatsand vegetable oil, and many organic acids are formed in the body during the
beakdown of foods.
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Acidity of Carboxylic Acids
Carboxylic acids are generally weak acids and establish equilibria in aqueous
solution with carboxylate anion, RCOO-.
Many carboxylic acids have about the same acid strength as acetic acid. Carboxylate ions are named by replacing the-ic ending in the carboxylic acid name
with ate.
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Acidity of Carboxylic Acids
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Acidity of Carboxylic Acids
Carboxylic acids react completely with strong bases such as sodiumhydroxide to
give water and a carboxylic acid salt.
Acetate ion, as the anion of a weak acid, is itself a base that can accept a proton
from HCl or some other strong acid.
Carboxylate anion can be converted back into free carboxylic acids by reaction
with acids
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Acidity of Carboxylic Acids
The interconversion of a carboxylic acid and its carboxylate ion is easily reversible
depending on yhe conditions. Which form is present depends on the pH of the medium and can be controlled
by adjusting the pH.
At low pH (acidic solution), carboxylic acid is present; at high pH (basic solution),
carboxylation ion is present:
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Reactions of Carboxylic Acids:Ester Formation
Esterification reaction, the reaction between an alcohol and a carboxylic acid to
yield an ester plus water.
Esterification reaction is carried out by warming a carboxylic acid with an alcoholin the presence of a strong-acid catalyst such as H2SO4.
In the reaction, an H is lost from the alcohol, an OH is lost from the acid, and
water is formed as a by-product.
The net effect is substitution of OR' for OH:
Esterification reaction are reversible and often reach equilibrium with substantial
amounts of both reactans and product present.
The goodyied are obtained either by using a large excess of the alcohol or by
continuously removing one of the products (LeChateliers principle).
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Some Common Esters
Aspirin is a white, crystalline solid thats a member of the group of drugs known
as salicylates (ester of salicylic acid).
Aspirin was found to be as effective a pain reliever but with fewer unpleasant
side effects.
Methyl salicylate is a counterirritant, a substance that relieves internal pain by
stimulating nerve ending in the skin for warmth, coolness, or pain.
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Some Common Esters
Glycerol Esters is a trihydroxy alcohol that form the backbone of natural fats and
oil when it is esterified with carboxylic acids that have long hydrocarbon chain.
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Reaction of Ester: Hydrolysis Hydrolysis, the breakdown of a compound by reaction with water; the Hs and O
from water usually add to the atoms in the broken bond in one way or another.
Esters undergo a hydrolysis reaction with water splits the ester molecule into the
carbocylic acid and alcohol combined inthe ester.
The net effect of the hydrolysis is a substitution of OH for OR'.
Ester hydrolysis is catalyzed both by acids and by bases.
Acid catalyzed hydrolysis is simply the reverse of the esterification reaction.
An ester is treated with water in the presence of a strong acid such as H2SO4 and
hydrolysis takes place.
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Reaction of Ester: Saponification
Saponification reaction, the reaction of an ester with aqueous hydroxide ion to
yield an alcohol and the metal salt of a carboxylic acid.
Base-catalyzed hydrolysis take place when an ester is treated with water in thepresence of a base such as NaOH or KOH.
The main difference between the acid- and base-catalyzed hydrolysis methods is
that the base-catalyzed reaction yields the carboxylate anion as a product rather
than a free carboxylic acid.
In order to isolate the acid, the anion has to be protonated by treatment with HCl
or H2SO4.
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Reaction of Ester: Claisen Condensation
Claisen Condensation Reaction, a reaction that joins two ester molecules to yield
a keto ester product.
A claisen take a place when an ester is treated with a strong base such as sodiummethoxide, Na+OCH3-, the sodium salt of methanol.
In the reaction, the OR' group is lost from the carbpnyl group carbon of one
ester molecules, and a bond forms between that carbon and the crbon atom next
to the carbonyl group of the second molecules.
The product is a ketone-ester, or keto ester.
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Reaction of Carboxylic Acids: Amide Formation
The reaction of a carboxylic acid with ammonia or an amine yields an amide, just
as the reaction of a carboxylic acid with an alcohol yields an ester.
In both cases, water is formed as a by-product, and the OH part of the carboxylic
acid is replaced.
The reaction of a carboxylic acid with ammonia or an amine to form an amide
doesnt take place, however, unless carbonyl OH group is first replaced with a
more reactive group.
In both cases, water is formed as a by-product, and the OH part of the carboxylic
acid is replaced.
In the laboratory, a compound called DCC (dicyclohexylcarbodiimide) is oftenused.
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Reaction of Carboxylic Acids: Amide Formation
Although the exact way in which DCC works is a bit too complex to discuss in
detail, its function is to activate the carboxylic acid by making it much more
reactive. One activated, the carboxylic acid then reacts rapidly with an amine to generate a
amide.
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Reaction of Carboxylic Acids: Amide Formation
The amide bond between nitrogen and a carbonyl-group carbon is the
fundamental link in protein molecules.
Some synthetic polymers such as nylon contain amide groups, and importantpharmaceutical agent such as acetaiophen.
Glutamic acid (glutamine), one of the natural amino acids, contain an
unsubstituted amide group, and urea which carries waste nitrogen from the body
is a diamide.
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Reaction of Amide: Hydrolisis
Amide undergo a hydrolysis reaction with water in the same way that esters do.
Just as an ester yields a carboxylic aci and an alcohol when hydrolyzed, an amide
yields a carboxylic acid and an amine. The net effect of amide hydrolysis is a substitution of OH for NH 2 or the
substituted amide nitrogen.
The cleavage of amide bonds by hydrolisis is the key process that occurs in the
stomach during digestion of proteins.
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Amide hydrolisis is catalyzed both by acids and bases.
If an acid catalyst such as HCl is used, the amine product is converted into its
ammonium salt as soon as its formed. If basic catalyst such as NaOH is used, the carboxylic acid product is converted
into its carboxylate ion.
Reaction of Amide: Hydrolisis
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Acid Anhydrides
Acid anhydride contain the RC=O, or acyl group, portion of two carboxylic acids,
both bonded to a central oxygen atom.
The acyl group may be from the same or from different acid, and the anhydridegroup may form between two carboxyl groups in the same molecule.
Because acid anhydride (RCO2OCR) react rapidly with water to regenerate acids,they are not found in plants and animals.
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Acid Anhydrides
Their reactivity, however, makes anhydrides useful in the synthesis of other
carboxylic acid derivatives.
The RCO portion of an anhydride combines with an alcohol to give an ester orwith an amine to give an amide, while the remainder of the anhydride adds
hydrogen to give an acid
Aspirin, an ester in which salicylic acid provides the OH group, is synthesized by the
reaction of salicylic acid and acetic anhydride
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Phospat and Esters Anhydrides
Phosphate ester, a compound formed by reaction of an alcohol with phosphoric
acid.
Nitrate ester, a compound formed by reaction of an alcohol with nitric acid.
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Phospat and Esters Anhydrides
Nitrate ester dont occur naturally, although nitroglycerin, a triester between
gltcerol (glycerin) and three molecules of nitric acid, is well known for its use in
the treatment of heart desease.
Phosphoric acid may be esterfied at one, two, or all three of its OH groups
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Phospat and Esters Anhydrides
Because they still contain acidic hydrogen atoms, the monoester and diester are
also acidic.
In neutral or alkaline solutions, including body fluids that are slightly alkaline, they
are present as ions:
Phosphate esters are widespeared throughout all living organism and are key
substances in nearly all metabolic pathway.
Glyceraldehyde-3-phosphate, is one of several phosphate esters that are
intermediates in the breakdown of carbohydrate to yield energy.
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Reaction of two molecules of phosphoric acid results in loss of water and produces
a phosphorus anhydride that reseambles carboxylic acid anhydrides but unlike
them still contains four acidic hydrogen that will be ionized in solution ofappropiate pH
Reaction of this compound, known as pyrophosporic acid (sometimes called
diphosphoric acid).
Phospat and Esters Anhydrides
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Phospat and Esters Anhydrides
Esters of pyrophosphoric acid and triphosphoric acid are referred to as
diphosphates.
In the following two methyl phosphate esters, note the difference between thePOC ester linkage and the POP phosphorus anhydride linkage.
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Organic Reactions
Equation for organic reactions tend to appear complicated.
The bigger the molecules reacting or the longer the series of reactions, the more
intimidating the equations. Many organic reactions have the same patterns, although organic chemists tend to
call them by different names.
For example, the addition reactions of alkenes, in which water (or halogens or
hydrogen halides) add across the double bond:
Elimination reactions, such as the elimination of water to give an alkene, are
essentially the reverse of addition reactions.
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Organic Reactions
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Organic Reactions