Conjugated systems

Question 1

what is an angstrom?

Answer 1

10^-10 metres

Question 2

what are conjugated double bonds?

Answer 2

alternating double and single bonds

Question 3

what does conjugation produce?

Answer 3

improves stability
changes structure
changes reactivity
spectroscopic behaviours given

Question 4

what is lycopene?

Answer 4

gives red colour by being conjugated contains antioxidants properties

Question 5

what are the characteristics of 1,3-butadiene?

Answer 5

double bonds are shorter than single bonds
electrons are delocalised
overlap between C-C bond giving partial double bond

Question 6

what does resonance hybrid show?

Answer 6

electron delocalisation
resonance stability
extended bond

Question 7

what is the relationship between conjugation and light absorption?

Answer 7

more conjugated a system the longer the wavelenth of light absorption

Question 8

show electrophilic aromatic substitution?

Answer 8

slide 17
lecture1-2

Question 9

what is the structure of benzene?

Answer 9

all carbons are the same length
they have partial double bonds
pie electrons delocalised around the ring

Question 10

how is aromaticity predicted?

Answer 10

Huckel’s rule

Question 11

what is Huckel’s rule?

Answer 11

4n+2= number of pie electrons

Question 12

how to predict aromaticity using Huckel’s rule?

Answer 12

if n= full number then aromatic molecule
if n= decimal then not aromatic

Question 13

what molecules does the Huckel’s rule apply to?

Answer 13

planar monocyclic rings
where each atom has a pie orbital

Question 14

what is the arrehenius definition of acids and bases and why its a limited definition?

Answer 14

acid increases concentration of H+ ions when dissolved in water
base increases concentration of OH- ion when dissolved in water
acid/base reaction is a neutralisation reaction
limited definition because water is needed as a solvent in liquid phase
requires only two ions

Question 15

what is the Bronsted lowry acid and bases definition and why its limited definition?

Answer 15

acid is a H+ donor
base is a H+ acceptor
limited by H+
always use for aqueous solutions

Question 16

what is the equation of autoionization of water?

Answer 16

slide 28
lecture 1-2
water both base and acid

Question 17

what is the lewis acids and bases definition and why its limited definition?

Answer 17

acid accepts an electron pair
base donate electron pair
acid/base reaction creation of a covalent bond

Question 18

what is a strong and weak acid?

Answer 18

strong acid fully dissolves in water releasing H+ ions
weak acid partially dissolves in water releasing H+ ion

Question 19

how to determine if an acid-base reaction is in completion or equilibria?

Answer 19

reactions using strong acid or strong base goes to completion and others are in equilibrium

Question 20

what is Kw at 25 degrees?

Answer 20

the ionisation constant of water
1* 10^-14

Question 21

what are the rules of autoionization of water?

Answer 21

if concentration of strong acid/base is more than 110^-6 then ignore water autoionization equilibrium
if concentration of strong acid/base is less than 110^-6 then water autoionization equilibrium needs to be acknowledged

Question 22

what reaction is used for weak acid?

Answer 22

Ka

Question 23

stronger Ka?

Answer 23

the larger the Ka the stronger the acid

Question 24

equation of Ka?

Answer 24

[A-]=[H+]
so
[H+]=square root(Ka*[HA])

Question 25

what is the pH equation for weak acids?

Answer 25

pH= 1/2 pKa -1/2log[HA]

Question 26

what equation is used for weak base?

Answer 26

Kb

Question 27

equation of Kb?

Answer 27

[OH-]= square root (Kb[B])
therefore:
[H3O+]=Kw/square root(Kb[B])

Question 28

equation for pKw?

Answer 28

pKw= pKa+pKb

Question 29

what is the equation of pH for weak bases?

Answer 29

pH=1/2pKw +1/2pKa +1/2log [B]

Question 30

what is the Henderson Hasselbach equation

Answer 30

pH=pKa +log [A-]/[HA]

Question 31

what is buffer pH?

Answer 31

‘function of it’s pKa and the ratio of concentrations of anion and acid, but the buffer’s capacity depends upon actual concentrations’