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The Organic acids
Teacher’s guide
The Organic acids
Learner’s guide
You can draw a correct structure for a organic acids.
The functional groups in a molecule help to define its reactivity.
The Organic acids
Learner’s activates
Introduction
Acidity of theories
Acidity of organic acids
Examples of interactions
Educator
Learners
Activates
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1
Organic chemistry is one branch from chemical, it is care to
study the carbon compounds and their derivatives.
Definitions acidities of compounds :
In organic chemistry we are frequently concerned with the
acidities of compounds that do not turn litmus red or neutralize
aqueous bases, yet have a tendency- even though small- to lose
a hydrogen ion.
In first, to define the acids according to the properties general
to those compounds,…………
2
Definitions acids.
Strong Acid donates H+ easily. Weak Acid has more
difficulty donating H+.
Examples.
CH3CO2H + H2O= CH3CO2¯ + H3O+
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The Definition of an acidic Solution
We define an acidic Solution as one where the
[H+] in the solution is greater than the [H+] in
pure water.
Acidic solution [H+] > 1.0 x 10-7 mole/L at 298.2
K.
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Acid Strength and Equilibrium Constant
For the following weak acid according to the Law of Chemical
Equilibrium:
HA + H2O = H3O+ + AIonization constant = Ka = [H3O+] [A-] / [HA]
The larger the value of Ka the more Hydronium ion will be in the
solution for a given initial concentration of the acid since the value
of Ka must equal the ionization expression on the right side of the
above equation and the Hydronium ion concentration is in the top
portion of that expression. The percentage of ionizations will
therefore be larger. Strong acids have Ka's that approach infinity in
value. Therefore the percentage of ionization would approach 100%
for strong acids.
Lewis Theory
Bronsted-Lowry theory
Arrhenious theory
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Lewise Theory
1
Lewis acid is an electron-pair acceptor.
Basic
acid
One advantage of the Lewis theory is the way it complements
the model of oxidation-reduction reactions. Oxidation-reduction
reactions involve a transfer of electrons from one atom to
another, with a net change in the oxidation number of one or
more atoms.
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2
The Lewis theory suggests that acids react with bases to
share a pair of electrons, with no change in the oxidation
numbers of any atoms.
Examples: the subject to interaction base and acids
according to this theory:
1- Equal compound with ion negative interaction:
BF3 + F: = BF4
2- Ion negative with ion positive interaction:
H+ (aq) + OH: (aq) = H2O
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Which of the following compounds can be Lewise acids?
1-AlCl3
2-NH3
3-Cl-
correct
3
1
Bronsted-Lowry theory
Acids donate H+ ions to another ion or molecule, which acts as
a base.
There are two ways of naming the H+ ion. Some chemists call it a
hydrogen ion; others call it a proton. As a result, Brønsted acids
are known as either hydrogen-ion donors or proton donors.
Examples.
+
HCl + H2O CH3O + Cl¯
+
CH3COOH +H2O=CH3COO¯ +H+
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The Acid Strength according to this theory, depend to
ability to lose the protons, thence the acid strong to
change at interaction to attendant base, the opposite is
right.
2
Which of the following compounds can be Brønsted acids?
a) H2O
(b) NH3
(c) HSO4(d) OHMenu
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Conclusion.
The Lowry-Bronsted definition is quite adequate for the
chemistry of acids and bases in aqueous solution. The
Lewis definition is useful because it allows us to
classify so many substances as acids or bases, and
because it provides an understanding of the details of
many chemical reactions.
Arrhenious theory
Arrhenious: acids are ionization in water to produce hydrogen
aqueous atom [H+ [aq]].
Although, after that has been found that hydrogen defiant with water
molecule to formed another ion to call hydronium ion {H3O+ [aq]}
HCl + H2O H3O+ [aq] + Cl¯[aq]
Therefore, the substances, which to applied the Arrhenious’ role:
1-
Contain the hydrogen element [H].
2- Dissolve in water [H2O] and their solution aqueous ability to
reach electricity by different degree.
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1
Questions
Fill in space:
Lewis was said acids are an electron pair acceptor.
Acids are Proton donor, the Scientist told
that……………………….
1-Arrhenious
2-Bronsted
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3- Lewis
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Acidity of Organic acids
Alkane and Alkyne and Alkene
Alcohol and Phenol
Aldehydes and Ketones
Carboxylic acids
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Organic acids
The organic acids are weak in the sense that this
ionisation is very incomplete. At any one time, most
of the acid will be present in the solution as unionised molecules. For example, in the case of
dilute ethanoic acid, the solution contains about
99% of ethanoic acid molecules - at any instant,
only about 1% have actually ionised. The strengths
of weak acids are measured on the pKa scale. The
smaller the number on this scale, the stronger the
acid is.
Acidities of Aliphatic Hydrocarbons
Background:
The acidity of the aliphatic hydrocarbons increases as
the character of the hybrid orbitals increases. An sp3
orbital has a 25% s character; an sp2 has 33% s
character, and an sp orbital a 50% s character. A base
but not the hydrogens of an alkene or an alkane can
abstract the hydrogen of a terminal alkyne.
Alkanes and Alkynes and Alkenes
1
1-
Alkanes:
Alkanes are molecules with only carbon-carbon single bonds,
therefore it are inactive chemical classification.
Hydrocarbons very weak acids and a very strong base can
remove proton to produce carbanion (carbon with negative
charge)
H
H
H
C
H + Base
H
C
_
+
+ Base-H
H
H
v. weak acid
v. strong conjugate base
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PKa’s of hydrocarbons ~62; very weak acids.
to define the acidity of alkanes comparison with another
compound, if those compound contain hydrogen atom more
acidity than Hydrocarbons’ hydrogen atom.
Example:
Rmg+ X¯ + H:O:H RH +RO¯ +Mg 2+ + X¯
Strong
Strong Weak Weak
acid
base
base
acid
RH weak Conjugate acid is, also alkane.
2
3- Alkenes:
Alkenes are molecules with one or more carbon-carbon double
bonds [R-CH= CH].
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2- Alkyne
Alkynes are molecules with one or more carbon-carbon triple
bonds (RC C- R).
Acidity of Terminal Alkynes:
The explanation for the correlation of bond length and
acidity with is that both are related to the hybridization of
the carbon orbital used for C-H bonding. Because (s)
orbitals are lower in energy than (p) orbitals, a hybrid
orbital with more s character will be lower in energy and
closer to the nucleus than will a hybrid with less s character.
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The lower energy orbital will be more electronegative and will
hold a proton tighter and also be better able to stabilize a negative
charge when a proton is removed in an acid-base reaction.

H–CC–H H+ +HCC
 26
K a = 10
Examples:
R-CC-H + NH2⇨ R-CC:¯ + NH3
R-CC-H + NaNH2→ R-CC:¯ Na + + NH3
Alkynes are stronger acid than alkenes and alkanes.
4
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Alcohol and Phenol
1-Aliphatic Acidity of Alcohol:
RO-H
primary alcohols
RRO-H
secondary alcohols
RRRO-H
tertiary alcohols
Alcohols are organic compounds that possess one or more -OH
groups attached to a hydrocarbon group (a group that contains
only carbon and hydrogen).
We learned earlier that alcohols are acids, too, and again of
roughly the same strength as water. Hydrogen bonded to the very
electronegative element oxygen.
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The polarity of the O-H bond facilitates the separation of a
relatively positive proton; viewed differently, electronegative
oxygen readily accommodates the negative charge of electrons left
behind.
ROH+ H2O  RO¯ +H3O+
Ka = [H3O]+ [RO]¯/ [ROH] [H2O]
Then, the Equilibrium constant value :
PKa = - log Ka
The alcohols acidity depend on alcohols’ kind, so primary alcohols
(RCH2OH) the stronger acid than secondary alcohols (RRCHOH),
these are stronger acid than tertiary alcohols (RRRCOH), because
of for return to the group alkyl related to carbon atom, that related
to (OH) group, whenever electrons density to increase on the
oxygen atom, then to find difficulty to ionization bond (O-H),
thence the acidity of alcohol is become little.
The acidity of alcohols is appear by their reaction with active
metals liberate hydrogen gas and from alkoxides.
ROH + Na RO¯Na+ +½ H2
A sodim alkoxide
2- Phenol:
OH
2
Phenols have an -OH group attached directly to a benzene
ring. Phenol itself is the simplest of these with nothing else
attached to the ring apart from the -OH group.
Acidity of phenols
Phenol (old name "carbolic acid") is a very weak acid, Ka 1.1 x 10-10.
This is about a million times stronger than water and aliphatic
alcohols, but about a million times weaker than aliphatic carboxylic
acids.
Phenols are reactions as weakly acids, it is dissolve in water to
give proton ion and phenoxide ion.
:Ö:H
:Ö:¯
+ H2O 
+ H+
Phenols get this acidity from the ability of the conjugate base
(phenoxide) to accomodate the negative charge by delocalization out
over the aryl ring (producing four resonance structures in
all). Substitutents, like electron withdrawing groups in particular,
enhance this ability, and produce even stronger phenolic acids.
:Ö:
:Ö
:Ö ¯
:O:
║
:
:O:
║
¯
║
¯
..
¯
:
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Aldehydes and Ketones
1
Aldehydes and Ketones are contain the carbonyl group.
Acidity α-hydrogen:
Carbonyl group to have two strong poles from electronic
in π bond, and that to be formed move aside by direction
the oxygen atom, that have more electronegative,
therefore the carbonyl carbon atom to be formed deficient
electron, this property to become
Carbonyl carbon is to work on strong the acidity of
hydrogen atoms, those connections by hydrogen atom,
that connection by α – carbon atom.
Carbonyl compound is containing upon proton, it is carbocatune by
resonance to be stable.
..
C= O..
>C=:O:
H
found the carbonyl compound is contain on α – hydrogen react to
base OH¯ will given Enolates ion,it is consisting in resonance
Hybird:
Ketones are lower acidity than aldehydes, although it is include upon
carbonyl group, because it is emptiness from hydrogen activity or
movement.
The basic is more use to define the acidity of α- hydrogen by use
hydroxyl ion.
CH3-Cyuyuuiuioopp[p[[]
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1
Carboxylic acids
Carboxylic acids are a class of organic compounds which contain
the carboxyl functional group. They are the most common class
of acidic organic compound.
O
O
R
C OH
Carboxylic
Acid
R
C O
+ H
Carboxylate
ion (named like
Acyl part of an
ester).
Carboxylic acids are, by definition, Bronsted acids that can
donate a proton to there species with lone pairs.
carboxylic acids are much more acidic than alcohols (pKa = 1618). One explanation for this is the resonance delocalization
afforded by the carbonyl group:
The carboxyl functionality is a compound functional group, containing
both a carbonyl functionality and a hydroxyl functionality. However, this
compound functionality is very different from either an alcohol or a
ketone.
Because the carbonyl and hydroxyl groups are directly attached to one
another, there is a strong resonance interaction between the two
groups, which sharply modifies the properties of the compound
functionality from that of either of the two component functionalities.
What is the reason for the much greater acidity of the OH protons of a
carboxylic acid than those of an alcohol? Primarily the resonance
stabilization of the conjugate base of a carboxylic acid, i.e., the
carboxylate anion. Recall that there are two equivalent resonance
structures for this anion, so that resonance stabilization is especially
strong.
General Questions
CH2=CH2 is call:
1-Propane .
2- Ethanol .
3-Ethylene.
1
2
Acidity Discovery
discovery to formalic or oxalic Acidity.
discovery to phenols Acidity.
discovery to formalic or oxalic Acidity.
Presentation test chemistry
discovery to phenols Acidity.
Presentation test chemistry
1. ArOH + OH
1- ArO + H2O
2- ArO2 +H2O
3- ArO + H3O
2- ArO is
•Stronger acid
•Weaker acid
Hydrocarbons very weak acids and a very strong base
can remove proton to produce carbanion (carbon with
negative charge).
Alkynes are stronger than alkenes or alkanes, but still
weak acids…weaker than carboxylic acids and alcohol.