exam one: ethers, epoxides, conjugated systems

Question 1

what is the hybridization of the O atom in an ether?

Answer 1

sp3

Question 2

if an ether is cyclic, can a nucleophile react with it?

Answer 2

no, it cannot react with the ether if the carbon is attached to it directly

Question 3

are ethers hydrogen bond acceptors or donors?

Answer 3

acceptors

Question 4

what are ethers unreactive to?

Answer 4

strong bases like NaOH

Question 5

how to name simple ethers using common name?

Answer 5

name both alkyl groups bonded to the O, and arrange alphabetically
- if symmetrical, add di

Question 6

how to name complex ethers using IUPAC

Answer 6

longer alkyl group is the hydrocarbon chain
other alkyl groups are substituents
simpler alkyl group gets changed from -yl to -oxy
if ring, add cyclo
ALPHABETICAL

Question 7

naming epoxides

Answer 7

o is substituent called an epoxy

Question 8

NaH

Answer 8

forms an alkoxide (O-), aka deprotonates OH

Question 9

Na or K

Answer 9

deprotonates OH

Question 10

what do phenyl ethers get deprotonated with?

Answer 10

NaOH

Question 11

silyl ethers

Answer 11

protecting groups for alcohols and F removes silyl ethers and replaces the alcohol

Question 12

ether cleavage by HBr and HI for phenol

Answer 12

only reacts once because it cannot attack a carbon directly connected to a phenol because it is a sp2 hybridized

Question 13

unsymmetrial epoxides under acidic conditions

Answer 13

are regioselective at the more substituted carbon

Question 14

base catalyzed epoxide ring opening for unsymmetrical epoxides

Answer 14

nucleophile attacks the less substituted carbon

Question 15

conjugated dienes

Answer 15

2 alkenes separated by one sigma bond

Question 16

what is the most stable conformation of a diene?

Answer 16

s-cis and s-trans

Question 17

allylic carbon

Answer 17

directly attached to sp2 carbon (double bond)

Question 18

can allyl carbocations be conjugated

Answer 18

yes and they are very stable, more stable than primary carbocation

Question 19

what addition product is faster?

Answer 19

1,2 addition - kinetic product

Question 20

what product is more stable?

Answer 20

1,4 - thermodynamic = more stable but slower

Question 21

what reagent is used for allylic bromination?

Answer 21

NBS (adds bromine)

Question 22

what needs to be paired with NBS for it to react?

Answer 22

light, heat or ROOR (Acid)

Question 23

where does the Br form when using NBS?

Answer 23

forms on the allylic carbon (carbon next to the double bond)

Question 24

allylic halides

Answer 24

good electrophiles in SN2 reactions, nucleophile attacks the carbon with the halide on it and the halide leaves

Question 25

H2SO4

Answer 25

gives proton to the anion

Question 26

what do dienes in diels-alder reactions have to be for it to react?

Answer 26

cis

Question 27

what type of diene is very reactive?

Answer 27

s-cis 1,3 diene

Question 28

what increases the rate of the reaction of a dienophile?

Answer 28

electron withdrawing substituents attached to it

Question 29

what makes a diene in a diels-alder more reactive?

Answer 29

electron donating groups attached directly to it

Question 30

what happens when an acyclic diene reacts with a cyclic dienophile?

Answer 30

cis-fused bicyclic product

Question 31

what happens when a cyclic diene reacts with an acyclic dienophile?

Answer 31

gives a bridged bicyclic product

Question 32

what transition states must diels-alders be in?

Answer 32

ENDO (sticking straight down and away from bridge)

Question 33

how does a 1,4 product of diels alder form?

Answer 33

if the substituent is on the side

Question 34

how does a 1,2 product of a diels-alder form?

Answer 34

if the substituent is on the top or bottom

Question 35

diels alders are ______ reactions

Answer 35

concerted and NO INTERMEDIATES

Question 36

HOMO

Answer 36

highest occupied molecular orbital

Question 37

LUMO

Answer 37

lowest unoccupied molecular orbital

Question 38

longer wavelength =

Answer 38

lower energy

Question 39

as # of conjugated pi bonds increase, what happens?

Answer 39

absorbtion gets shifted to longer wavelength, meaning lower energy

Question 40

where does the promotion of electrons to an excited state occur in conjugated dienes?

Answer 40

lower wavelengths

Question 41

what type of radicals are the most stable?

Answer 41

primary allylic

Question 42

for allylic radical to react, what has to be present?

Answer 42

light, heat or peroxides

Question 43

MO for allylic radicals

Answer 43

lowest energy: 2 bonding pairs (same signs) middle: nonbonding (opposite signs) - 2 orbitals and 1 node highest: antibonding (all opposite signs) - 2 nodes

Question 44

if there are two alkenes but one is apart of a benzene ring, is it conjugated?

Answer 44

no it is not because the alkene apart of the benzene ring is its own system

Question 45

what does UV radiation need for it to be absorbed?

Answer 45

a conjugated pi system so conjugated dienes

Question 46

what do dienes need to react in a diels-alder?

Answer 46

1. has to be cis or adopt one 2. more electron donating groups, the more reactive

Question 47

if a diene is locked in cis form, it is ______

Answer 47

more reactive

Question 48

if a diene is locked in trans, it is _____

Answer 48

not reactive at all

Question 49

what type of reaction is a williamson ether synthesis?

Answer 49

SN2 meaning it causes inversion of stereochem and attacks from BACK

Question 50

MCBPA reacting with _____ substituted alkene reacts faster

Answer 50

more

Question 51

what does MCBPA do?

Answer 51

form epoxides

Question 52

what does CH3CH2MgBr do?

Answer 52

attacks at LESS substituted carbon and breaks epoxide

Question 53

what does NBS do?

Answer 53

brominates

Question 54

if two substituents are ENDO in a bicyclic bridged ring, are they cis or trans?

Answer 54

CIS

Question 55

what happens when an oxyanion attacks a halide in an SN2 reaction on a cyclic ring?

Answer 55

when the oxyanion attacks the chloride, it forms an epoxide with the carbon