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Bronsted acids:
- AceDONA ++
- Substance that DONATES H+ protons
- Molecule that GIVES the H+
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Bronsted BASE:
- BASS(ept) ++
- Substance that ACCEPT H+ ions
- H+ Acceptor
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Lewis Acid:
- Lewis Accepts Electrons
- Substance that ACCEPTS ELECTRONS
- If the molecule is accepting electrons, it?s a LEWIS ACID
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Lewis Base:
Substance that DONATES ELECTRONS
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Conjugate base
The product that comes from the ACID (looks like the acid but with a neg charge replacing H)
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Conjugate ACID
Product that comes from base, just with one proton added & increase charge by +1
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Amphiprotic or amphoteric def
Substance that can behave as EITHER ACID or BASE
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Base/acid/conjugate strengths relationship
- STRONGER (more reactive) the acid, the WEAKER (more stable) the conjugate base
- STRONGER the BASE, weaker the conjugate acid
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pKa relationship
- Ka goes up = pKa goes down = acid strength goes UP
- Same with strength and relations of bases (Kb, pKb, Base)
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Sorting acids and bases by strength nmeumonic
- CARDIO
- Charge
- Atom
- Resonance
- Dipole Induction
- Orbital Hybridization
- Start at C and the rest are in order of importance
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Charge (CARDIO)
- The more POSITIVELY charged, the more ACIDIC
- H0- < H20 < H30+ Most acidic
- The smaller the pKa, the more ACIDIC
- More Negatively charged the compound formula is?the more BASIC! *think the more reactive conjugate base is the more NEG charged (ie: Cl- is conjugate base)
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Atom (CARDIO)
- As you go LEFT to RIGHT on periodic table, ACIDITY INCREASES: due to increasing electronegativity
- Ie: CH4 less acidic than HF (F on the right of C)
- ACIDITY INCREASES as you go DOWN on the periodic table: Increasing size of atoms lead to more acidity eventhough they are opposite trend of electronegativity
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Resonance (CARDIO)
- The more stable the CONJUGATE base, the stronger the acid
- IE: Resonance increases stability, so if can replace acidic HYDROGEN with NEGATIVE charge to get its conjugate base and the resonance makes it more stable, so it is a strong acid!
- The more stable the Conjugate ACID, the stronger the base
- Easier it is for the acid to donate protons (Bronsted acid)
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Dipole induction (CARDIO)
- If you have electron WITHDRAWING groups (ie electroneg groups), they INCREASE ACIDITY
- Usually have electronegative groups, such as F, Cl, Br, I, N, O PULLING the ELECTRONS towards itself
- Presence of acidic molecule sucking electrons away from a hydrogen, allowing for the base to take the hydrogen
- If there are lone pairs or ability for electrons to be donated, makes it more difficult for the Hydrogen to be taken away from molecule
- If you have electron donating groups, they DECREASE ACIDITY
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***Dipole induction and BASICITY
- Base is something with basic electrons, bonds that will form with the H+
- Withdrawing groups DECREASE atoms basicity because they make the basic electrons less available
- Donating groups make it MORE BASIC as they make it more available for the electron (ie O-) to move out and bond to Hydrogen
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Orbital Hybridization (CARDIO)
- The more closer the s orbitals are to the nucleus, the more they are closer to the protons and therefore more electronegative: wants to accept electrons more (MORE ACIDIC) if sp vs sp3
- Therefore, SP is the most ACIDIC, followed by sp2, then sp3
- Look at the carbon hybridization attached to the hydrogen
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To Draw conjugate base of any acid
- Remove a Proton (H) to the acid and decrease its charge by +1 (usually is negative)
- Ie: HCl is the acid?remove the H and becomes Cl-
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To draw conjugate ACID of any base
- ADD a proton (H) to the base and INCREASE its charge by +1
- IE: H20 is the base?add a proton and becomes H30+
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Amino acids
- Carboxylic acid (CO2-) and an AMINE part (NH3+) with neg and pos existing at pH7: Zwitterion
- Difference is in the R side chains
- Carboxylic acid is more acidic than amine, so will always lose the carboxylic hydrogen before NH3
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Pka value and acidity
LOWER pKa, the MORE ACIDIC the proton
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As decrease pH, and become more acidic, what happens to H+
- Increase the amounts of H+ atoms in the solution
- Bottom Line: Lower the pH, More pRotonated
- Amino acids will exist in more of the CHO2 and NH3+ form
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If pKa is LESS than pH in solution, what happens to its protons
- They will be DEPROTONATED
- More OH in the solution compared to the pKa, which is a strong acid, so will lose some protons
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If pKa is MORE than the pH in the solution, what happens to its protons
- Becomes PROTONATED
- High solution pH means more protons in solution, and if it?s a weak acid (HIGHER pKa) then the acid will get PROTONATED
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