Influence of electronic and structural effects on acidity

Question 1

what happens when there’s an decrease in pKa (increase in electronegativity)?

Answer 1

increase in acidity
more stabilization of conjugate base

Question 2

what are the inductive effects of electron-withdraw groups equilibirum?

Answer 2

stabilizing of the molecule

Question 3

what is the inductive effect of electrons being donated in an equilibrium?

Answer 3

destabilizing of the molecule

Question 4

what do electron withdrawing groups do to the acidity?

Answer 4

increase it

Question 5

what does increasing the halogen atom do to the acidity?

Answer 5

increase in acidity
one chlorine increases acidity by a factor of 100
increasing the inductive effect

Question 6

what is trichloroacetic acid?

Answer 6

strong acid

Question 7

what are the electron donating groups?

Answer 7

opposite effect
increases electron density
destabilizing conjugate base
therefore forming weaker acid

Question 8

what are the most common electron donating group?

Answer 8

alkyl groups

Question 9

how does hybridization effect acidity?

Answer 9

the hybridization of carbon atom attached to acidic H effects acidity
the more S orbital an atom has the closer it is to the nucleus so more electronegative, and more acidic and more stable

Question 10

which are more electronegative: sp, sp2, sp3?

Answer 10

sp most
sp2
sp3 lowest

Question 11

how is delocalization of charge in base a stabilising factor?

Answer 11

through resonance

Question 12

effect of halogen group in a benzene?

Answer 12

the closer it is to the carboxyl group the lower the pKa

Question 13

effect of nitrophenols in benzene with ortho or para names?

Answer 13

further delocalization of acidic charge
increasing acidity

Question 14

is m-nitrophenol less acidic for having a higher pKa than o-nitrophenol and p-nitrophenol?

Answer 14

no because inductive effect helps stabilize the anion

Question 15

effect of more nitroxide groups on a phenol?

Answer 15

if there are more nitroxide groups on a phenol the more acidic it is

Question 16

what is a base?

Answer 16

will accept a proton by donating a pair of electrons

Question 17

how do we measure the strength of a base?

Answer 17

using the pKa of its conjugate base

Question 18

what is the difference between a strong base and a weak base?

Answer 18

strong base has a small Ka and large pKa
weak base has a large Ka and small pKa

Question 19

what is bascicity?

Answer 19

‘ability of a compound to use its non bonding electrons to bond with a proton’

Question 20

what makes an acid stronger?

Answer 20

increasing stability of conjugate base
favouring loss of proton from acid

Question 21

what is a more stable base?

Answer 21

a weaker base

Question 22

what is more ready to donate electrons to a proton, anionic base or neutral base?

Answer 22

anionic base

Question 23

what happens to basicity as atom becomes more electronegative in a compound?

Answer 23

basicity decreases as atom becomes more electronegative

Question 24

what makes a base stronger?

Answer 24

increasing stability of conjugate acid

Question 25

what does H-bonding do to the positive charge on nitrogen compounds?

Answer 25

H-bonding stabilizes cations

Question 26

what does increasing acidity do?

Answer 26

increases stability of conjugate base

Question 27

how does stabilizing the conjugate base make a weaker base?

Answer 27

discourages protonation making it a weaker base

Question 28

what does more stability mean about the base?

Answer 28

the more stable a base the weaker the base

Question 29

what does delocalized elctrons mean about the basicity

Answer 29

if electrons are delocalized the less basic the compound is

Question 30

what is the inductive effect of methyl addition to nitrogen?

Answer 30

increases basic strength

Question 31

what happens when 2nd and 3rd methyl groups are added to ammonium?

Answer 31

2nd methyl group added causes a smaller effect on the pka 3rd methyl group added reduces basicity

Question 32

what is the effect of electron withdrawing groups?

Answer 32

decrease electron density which destabilizes conjugate acid making it less likely to pick up a proton making the base weaker

Question 33

relationship between acidity and p character?

Answer 33

the acidity of the of C-H decreases as the p character increases

Question 34

why is it harder to protonate in sp orbital than sp3?

Answer 34

electrons held closer to nucleus in sp orbital so harder to protonate than if in sp3 orbital

Question 35

what happens in the delocalization of charge of conjugate base of anions?

Answer 35

stabilizes anion increase in ionization of anion

Question 36

what happens when delocalization of base happens?

Answer 36

stabilizes base reducing basicity

Question 37

when does resonance stabilization occur with an amide?

Answer 37

with O-protonated amide (where H has attached to oxygen) not with N-protonated amide (where H has attached to nitrogen)

Question 38

how does resonance stabilization occur in O -protonates amides?

Answer 38

lone pair on nitrogen is able to overlap into p system

Question 39

how does resonance stabilization occur in amidines?

Answer 39

the nitrogen replacing oxygen becomes protonated allowing stabilization of cation

Question 40

what are the properties of amidines?

Answer 40

strong bases

Question 41

what are guanidines?

Answer 41

stronger bases than amidines

Question 42

what makes aniline a weak base?

Answer 42

resonance occurs in an uncharged amine

Question 43

how does the effect on aromatic ring increase

Answer 43

effect increased if electron-withdrawing group on ortho or para position on the aromatic ring

Question 44

why do aromatic amine are a weaker base than aniline?

Answer 44

improved delocalization in free base

Question 45

what effect do electron-donating groups have?

Answer 45

increase basicity

Question 46

why does pyridine have a lower basicity than piperidine?

Answer 46

pyridine is aromatic with 6p electrons planar lone pair of electrons held in sp2 orbital so increased s orbital than piperidine meaning lone pair of electrons are held closer on nitrogen so less readily bonded to a proton

Question 47

why is pyrrole is a stronger acid than pyridine?

Answer 47

the lone pair is part of the delocalized p-system and not available to bond to a proton

Question 48

what happens when a halogen is more electronegative?

Answer 48

greater inductive effect will effect acidity more making the molecule more acidic

Question 49

what effect does placing the electron-withdrawing group have on pka when its located further from the negative charge?

Answer 49

less inductive effect because the electrons have to transmitted through more bonds

Question 50

how is the acidity of C-H groups adjacent to carbonyl increased?

Answer 50

resonance stabilization

Question 51

why does adding a 3rd methyl group to nitrogen reduce basicity?

Answer 51

because the pka is measured in aqueous solution so there's H-bonding which stabilizes the positive charge on the nitrogen and the more alkyl groups added the less this has an effect