chapt 4 acids, bases and intro to reactions

chapt 4 acids, bases and intro to reactions - Types of...

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Types of Organic reactions: Addition reaction : A + B C Elimination reaction: A B + C Br H H H H H C C H H H H + HBr NaOH Atoms are removed and a Pi bond is formed C C H H H H + HBr Br H H H H H Atoms are added to the molecule and a Pi bond is broken
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Types of Organic reactions: Rearrangement reaction: A B Reactant is rearranged to give an isomeric product C C H CH 3 H 3 C H Acid catalyst C C H H H 3 CH 2 C H Substitution reaction: A-B + C-D A-C + B-D Cl H H H H H H H + Cl-Cl HCl + Light Here the Pi bond moved from being between C1 & C2 to C2 & C3
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Br ø nsted-Lowry ACID: any species that can donate a proton BASE: any species that can accept a proton Lewis ACID: a species that can accept electron pairs to form new bonds BASE: a species with electrons that can be donated to form new bonds electrophile nucleophile Nucleophiles and electrophiles are common reactants in organic reactions Wade 7 th edition chapter 1 sections 12 & 13
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Br ø nsted-Lowry - Conjugate Acids and Bases when an acid donates a proton it can now accept a proton back making it a base + + - - + + + + Wade 7 th edition chapter 1 section 13
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Brønsted-Lowry acid strength is defined by the extent of ionization in H 2 O HA + H 2 O H 3 O + + A - Conjugate acid-base pair acid base K a K a = [H 3 O + ] [A - ] [HA] K a is the acid dissociation constant the LARGER the K a is the STONGER the acid is (K a > 1) Usually expressed as pK a the LOWER the pK a the STRONGER the acid pK a = -log 10 K a Wade 7 th edition chapter 1 section 13A
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Br ø nsted-Lowry Base Strength is inversely related to the strength of its conjugate base The conjugate base of a strong acid is a weak base. pK a + pK b = -log 10 -14 = 14 Water ion-product constant A strong acid reacts and forms a weak conjugate base. A weak acid reacts and forms a strong conjugate base. Reactions favor formation of the weaker acid or base. Wade 7 th edition chapter 1 section 13B
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Factors that influence acidity - Electronegativity – the more electronegative an atom is the better it is at holding a negative charge Most acidic H-F + H 2 O H 3 O + F - least basic H-O + H 2 O H 3 O + O - H-N + H 2 O H 3 O + N - least H-C + H 2 O H 3 O + C - most basic acidic + + + + Wade 7 th edition chapter 1 section 13C
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Factors that influence acidity - size – the larger the atomic radii is the more space there is for the negative charge to spread over I > Br > Cl > F - resonance – if the negative charge can spread out over more than One atom then the negative charge is more stable (making a weak base) for example: a carboxylic acid (COOH) will become a carboxylate ion (COO - ) after it reacts as an acid OH O + NH 3 O O + NH 4 Wade 7 th edition chapter 1 section 13C
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Acidity - Decide what proton is going to be donated - What proton (H + ) is going to be lost is determined by size & electronegativity of the atom bound to H Look at the conjugate base produced - Does one structure have more possible resonance structures
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chapt 4 acids, bases and intro to reactions - Types of...

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