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Chapter 3: Acids and Bases
What's Covered? Types of Acids/Bases Identify Conjugate acid/bases Draw Acid/Base mechanisms Determine products and equilibrium Use pKa Values
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Types of Acids/Bases:
Bronsted-Lowry definition Acids donate a proton,H Basesacceptaproton Alss Lewis Acio HO 5- :15: H H Acid Base conjugate (proton donor) (proton acceptor) conjugate (base acidy Lewis acid/base definition A Lewis acid accepts a pair of electrons - A Lewis base donates a pair of electrons
B
H
Base
1
Curved Arrows in Acid/Base Reactions
What is an acid/base mechanism?
ae ie Thebaseattacksthe acidtusing a pair of electrons Nat The acid cannot lose its proton without the base taking it. All charges should be balanced in the reaction, a + charge with a -- charge to form a B neutral solution. H i5 NOf StaY bY you8sclF Watch out for spectator ions (NatMg*2,CI-etc) The acid/base mechanism shows two arrows indicatingthat two pairs of electrons move
A:
simultaneously
Electrophile: Acid get Atached Electron loving, gets attacked Electron Poor, empty orbital, &+ or + charge V-H3
Nucleophile:Base Seeking positive, attacks with 2 electrons Electron Rich, - or - charge
H H Curved Arrows in Acid/Base Reactions:
Example:
H Base
HOH
Acid
conjugate base
conjugate
(proton donor) (proton acceptor)
Try it On Your Own! Draw the curved arrow mechanism. Label the acid, base, conjugate acid and conjugate base.
HO:0 Conj. Base
H .O.
Base
Consi Acid
Acid
2.
Curved Arrows in Acid/Base Reactions:
AnswerTry it On Your Ownl Draw the curved arrow mechanism. Label the acid, base, conjugate acid and conjugate base
H O.
:0H
Cms. Base
Acid
Gms. acid
bast
-In the above reaction how willing was water to give up its proton? .How stable is the conjugate base? .Which side of the equilibrium is favored?
Quantifying Acidity and Basicity:
pKa values range from -10 to 50. Lower pka=stronger acid The stronger an acid the weaker its conjugate base.
VeaY Acidic %
i.
[OWexIKa- S+tongex cucid L.P.S.A 8 YAcid X
X. less Stabl