Quiz 5

Question 1

primary alkylated alcohol

Answer 1

C bonded to an OH, 2 Hs, and one R group

Question 2

secondary alkylated alcohol

Answer 2

C bonded to an OH, 1 H, and two R groups

Question 3

tertiary alkylated alcohol

Answer 3

C bonded to an OH and three R groups

Question 4

explain the IUPAC naming for alcohols

Answer 4

*the alcohol should always have the lowest number (it has priority)
*write the substituents in alphabetical order, as well as identifying the position of the -OH group

1. select the longest carbon chain and replace the end with -ol
2. number the alkyl chain beginning at the end nearest to the hydroxyl group

Question 5

how would you name a compound with two or three alcohols

Answer 5

diol = 2
triol = 3

Question 6

describe hydrogen bonding in alcohols and phenols (connect it to BP)

Answer 6

the attraction between the positively polarized OH hydrogen and the negatively polarized oxygen holds the molecules together. When you have a ton of hydrogen bonds (a bunch of OHs connected), these bonds have really high energy which gives them a high boiling point.

Question 7

phenol pka

Answer 7

9.89

Question 8

is phenol or alcohol more acidic

Answer 8

phenol because the negative charge in the phenoxide ion is not localized on the oxygen atom, as it is in an alkoxide ion, but is delocalized-it is shared by a number of carbon atoms in the benzene ring. Since it is attached to EWGs, these groups stabilize the ion and lower the pKa of the alcohol.

Question 9

why is the resonance stabilized phenoxide ion more stable than an alkoxide ion

Answer 9

because the negative charge on the oxygen can be delocalized throughout the ring.

Question 10

what is an alkoxide ion

Answer 10

An ion with a negative formal charge on oxygen atom bonded to an sp3 carbon atom

Question 11

what is a phenoxide ion

Answer 11

the conjugate base of phenol (has a -O)

Question 12

how are alkoxides formed

Answer 12

by reaction with alkali metals (li, Na, or K) OR by deprotonation with a strong base (H-)

Question 13

how to get an alcohol from an alkene

Answer 13

hydrobromination (1. BH3 2. H2O2, HO-)

Question 14

how to produce 1, 2 diols from alkenes (CIS OXYGENS)

Answer 14

1. OsO4 –> produces an osmate intermediate
2. NaHSO3 and H2O

Question 15

how to produce 1, 2 diols from alkenes (TRANS OXYGENS)

Answer 15

1. MCPBA and RCO3H –> produces the intermediate with a triangle and oxygen
2. H3O+

Question 16

what should you do first to convert alcohols into alkyl halides

Answer 16

alcohols must be ‘activated’ (protonated) by a strong acid before they can react

Question 17

describe reactions of secondary and tertiary alcohols to produce alkyl halides

Answer 17

TWO PATHS: Sn1 and E1rxn
reacts with HBr

1. acid protonates most basic atom
2. formation of carbocation
   3.
   For addition: reaction of the carbocation with a nucleophile
   For elimination: alkene product undergoes addition rxn

both paths obtain the same product

Question 18

what kind of intermediates are produced by Sn1 rxns

Answer 18

carbocation intermediates. These will rearrange to produce the more stable product, so watch out.

Question 19

describe the reaction for primary alcohols to produce alkyl halides

Answer 19

Sn2 rxn
reacts with HBr

1. acid protonates the most basic atom
2. backside attack by the nucleophile

(but there are better ways to convert primary and secondary alcohols into alkyl halides

Question 20

best methods to convert primary and secondary alcohols into alkyl halides

Answer 20

1. PBr3 —-pyridine—->
2. PCl3 —-pyridine—->
3. SOCl2 —-pyridine—->

all place alkyl group at the end

Question 21

explain the significance of sulfonate ester

Answer 21

(ex. tosylate) is a very good leaving group. it is also formed when an alcohol reacts with a sulfonyl chloride

Question 22

how does the way an alcohol is activated affect the configuration of the alcohol (inversions)

Answer 22

• in two step rxns, 2 inversions occur which gives you the same configuration you started with
• in one step rxns, one inversion occurs which give you the opposite configuration you started with.

Question 23

is a dehydration rxn reversible

Answer 23

yes

dehydration rxn (fwd) –> remove water
hydration rxn (rev) –> acid within the presence of an excess of water

Question 24

explain acid-catalyzed dehydration of an alcohol

Answer 24

• elimination rxn (double bond formed)
• needs strong acid catalyst such as H2SO4 or H3PO4 and heat

Question 25

is dehydration regioselective

Answer 25

yes, the major product is the more stable alkene (the most substituted alkene - Zaitsev’s Rule)

Question 26

why are tertiary alcohols the easiest to dehydrate

Answer 26

the rate of dehydration reflects the ease of carbocation formation

Question 27

what should you be careful of for E1 rxns

Answer 27

the formation of a carbocation, because rearrangements can occur.

Question 28

why don’t we do dehydrations with a primary alcohol

Answer 28

because a primary carbocation is very unstable. Since the E1 mechanism used for secondary and tertiary alcohols relies on a carbocation intermediate, a primary alcohol cannot follow the E1 mechanism

Question 29

describe dehydration under mild conditions for tertiary, secondary, and primary alcohols

Answer 29

reactants: POCl3 and pyridine –> eliminates

POCl3 is a good dehydrating reagant for primary, secindary, and tertiary alcohols because carbocation rearrangements do not occur.

Question 30

describe the oxidation of secondary alcohols

Answer 30

OH becomes O double bond using H2CrO4

Question 31

how to turn a primary alcohol into an aldehyde and then into a carboxylic acid

Answer 31

primary alcohol to aldehyde –> H2CrO4
aldehyde to a carboxylic acid –> further oxidation

Question 32

how do you have mild oxidation of primary alcohols

Answer 32

(how do you get the oxidation to stop at the aldehyde)
- one must use milder oxidants, such as PCC or Dess-Martin

Question 33

what are PCC or Dess-Martin used for

Answer 33

oxidize primary alcohols to aldehydes and secondary alcohols to ketones

Question 34

how do you oxidize a tertiary alcohol

Answer 34

you don’t