Don't want to forget (July 22nd)

Question 1

soluable hydroxides of group 1A and 1B are considered?

Answer 1

stong bases – Ca(OH)2

Question 2

between NH3 and CH3NH2 which is the stronger base?

Answer 2

CH3NH2 is stronger bc of the electron-donating group

- it donates electrond to N - therfore making it more electron dense and increasing its effectivness to pick up a proton

Question 3

EDG on acids

Answer 3

• make acids less acidic bc when proton leaves, there is a negative charge and EDG destabalize this charge by donating more electrons
• in comparasion EWG would increase acidity

Question 4

what does resonance do to basicity

Answer 4

decreases

Question 5

how can I determine if its an EWG or a EDG

Answer 5

steps:

1) circle the more electroneg atom

• if it’s closer to the ring = donating
• if its farther from ring = withdrawing

Question 6

how can we increase buffering capacity

Answer 6

increase the concentrations, even if ration stays the same- buf cap increases

Question 7

when should I recognize question is asking for HH or ka

Answer 7

• HH when wasnt to estimate pH or POH in a buffer system and you know concentrations of acid and conjugate base and pka
• when q asked for concentration og H3O and gives me Ka and M of the acid
• write acid dissociation, solve for x

Question 8

NMR (this shits cool)

Answer 8

• all protons are like tiny magnets, electrons circle around them - creat mag field (have to use thumb rule but with thumb in direction of current (opposite e))
• protons (or other atomic nuclei) have magnetic moments that are orientated at random

when external mag feild is applied this moments can align (alpha state) or oppose (B- higher energy - think like a compase needle being pushed opposite) - to get to this state need energy - if with hit the protons with a pulse of varying wavelengths some a–> b, when let go, will go back down - record this ! will show us the frequencies - which correspond to energy difference –> can use this to determine how sheilded or desheilded proton is

sheilded mean has electrons protecting it —> which have their own Bind –> and this will affect Baff –> affect energy change between 2 states

in summary, NMR is used to assess different envirmoents that protons are in - bc if they show the same f = same envirmoent, and integration ( the intestiy of signal) tell us how many

Question 9

a decreased Baff means

Answer 9

a decreased energy difference —> E=hf –> smaller frequency

• if H is sheilded it has a smaller frequency (shows up on the right side of f table)

Question 10

explain deshielding

Answer 10

the proton feels a greater energy difference because it doesn’t have a shield to make Baff smaller, therefore, larger B =larger E = larger f

Question 11

n +1 rule

Answer 11

n = number of protons proton neighbors

n+1 = the number of peaks

for example if proton has one proton neigh than it willlbe a doublet

Question 12

distance between 2 peaks

Answer 12

coupling constant (J), measured in Hz

Question 13

what is the chemical shift

Answer 13

& =the observed shift from the standard TMS signal / the f of the used spectrometer

Question 14

what has the highest f signal in H-NMR, why?

Answer 14

carboxylic group

far to the left = desheilded - it has lost its sheild of electrons bc of high electroneg groups

• this proton feels a large Baff= large energy change = large f

E=hf

Question 15

whats infrared spectrometry

Answer 15

principle= find functional groups by measuring molecular bond vibrations

graph is wavenumber of transmittance - and we know somecommon functional groups wavenumbers so on graph can determine what groups are in molecule

Question 16

O-H

Answer 16

3300 U shape

Question 17

N-H

Answer 17

3300 V shape

Question 18

C=O

Answer 18

1750 sharp

Question 19

what bonds vibrate faster- have a higher IR frequency

Answer 19

stronger bonds and lighter atoms

Question 20

ultraviolet spectroscopy

Answer 20

need pi bonds or lone pairs

• measures absorption of ultraviolet light which causes movement of electrons between MO
• to appear on graph - must have small enough energy difference between HOMO and LUMO

Question 21

the smaller the dif between MOMO and LUMO?

Answer 21

the longer the wavelength a molecule can absorb

bc E= hf c= f/\ —> E = hc divided by /\

E and /\ are inversely proportional

so if litter energy dif (easily excited) = large /\

Question 22

the conjugated system in UV spec

Answer 22

have unhybridized p-orbitals - can be excited by Uv light

they shift the absorbtion spectrum, resulting in max /\ at a higher value - sometimes even in the coloured spectrum ( this is why pigments are conjugated??). -YES