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Organic Chemistry > Ch. 9 - Alcohols, Ethers & Related Compounds (Week 1) > Flashcards

Ch. 9 - Alcohols, Ethers & Related Compounds (Week 1) Flashcards

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1
Q

Why are alcohols (basic)? What can they act as?

A

functional group that contains hydroxyl group bonded to sp3 carbon
- can act as nucs. bases or weak acids (pKa = 15)

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2
Q

What are enols and phenols?

A

enols and phenols have OH bonded to sp2 carbon

  • undergo different reactions
  • enols have OH bonded to C double bond
  • phenols have OH bonded to benzene ring
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3
Q

What are ethers? What is their reactivity?

A

two alkyl groups bonded to an oxygen

- relatively unreactive (polar aprotic solvent)

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4
Q

What is a symmetrical ether vs an unsymmetrical ether?

A

sym: same alkyl groups
unsym: diff alkyl groups

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5
Q

What are epoxides/oxiranes? What is their reactivity?

A

ethers with ozygen atom in 3-membered ring

- highly reactive due to highly strained 3-mem ring that wants 109.5 deg tetra angles but is stuck with 60 deg angles

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6
Q

What is the electron geometry of O in alc/eth/epox?

A

tetrahedral

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7
Q

What is the molecular geometry of alcohols and ethers?

A

bent, bond angles are 109.5º

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8
Q

What is the bond angle of an epoxide? What are the consequences of this bond angle?

A

60º, consequences are angle strain which makes epoxides more reactive

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9
Q

Which are polar: alc/eth/epox?

A

all are polar and exhibit dipole-dipole, alcohols capable of H-bonding

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10
Q

How are alcohols named using IUPAC?

A

1) find longest carbon chain bearing -OH group

2) number carbon chain to give -OH the lower number and apply normal nomenclature names

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11
Q

How are rings with alcohols named?

A

number ring beginning with OH group then give next lowest number to substituent
** “1” in name is omitted for OH

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12
Q

When are common names used for alcohols? How are they named?

A

simple alcohols

1) name carbon atoms of a molecule as if single alkyl group
2) add “alcohol” separated by space

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13
Q

How are common names assigned for ethers (simple ethers)?

A

1) name both alkyl groups bonded to O

2) arrange groups alphabetically and add “ether”

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14
Q

How are IUPAC names assigned for ethers?

A

1) name simpler alkyl group and oxygen as alkoxy sub and change ending of alkyl group to -oxy (ex. methoxy)
2) name remaining alkyl group as an alkane w/ alkoxy group as sub bonded to this chain (ex. 4-ehtoxyoctane)

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15
Q

What is a heterocycle?

A

any cyclic compound containing heteroatom (ex. THF)

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16
Q

How are epoxides named as epoxyalkanes?

A

1) name alkane chain/ring to which O is attacked
2) use prefix “epoxy” to name epoxide as sub
3) use two numbers to designate location of O
ex. 1,2-epoxycyclohexane

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17
Q

What does a bent structure mean in terms of IMFs for alcohols and ethers?

A

dipole-dipole interactions

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18
Q

What affects solubility of alcohols/eth/epox?

A
  • if they have less than or equal to 5 carbons, they are soluble in water (due to hydrogen bonding with O**check!)
  • if they have more than 5 carbons, they are insolubel in H2O
  • all are soluble in organic solvents regardless of size
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19
Q

T/F: A structure can be classified as an alcohol if it has OH bonded to an sp2 carbon.

A

False, alcohols must have OH bonded to an sp3 carbon.

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20
Q

T/F: Alcohols and ethers are common products of nuc sub reactions.

A

True

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21
Q

What is the conjugate base of an alcohol called?

A

alkoxide

22
Q

What is an aromatic alcohol called?

A

phenol

23
Q

What is an alkoxide?

A

R-O- (an alcohol without the hydrogen on OH), the conjugate base of an alcohol

24
Q

What happens in a Williamson ether synthesis?

A

An alcohol reacts with sodium hydride and then an alkyl halide to give an ether.

25
Q

What is the general mechanism for WES?

A

1) acid-base reaction btw alcohol and NaH

2) Sn2 btw alkoxide and alkyl halide

26
Q

What is a halohydrin?

A

an organic compound that has a hydroxy group and a halogen on two opposide but adjacent carbons, participates in intramolecular version of WES

27
Q

What is the base, nucleophile and electrophile in WES?

A 
base = NaH (generates alkoxide)
nuc = alkoxide 
elec = 1º or 2º alkyl halide or alkyl tosylate
28
Q

What is solvent type for WES?

A

polar aprotic (DMSO, MeCN, THF, DMF, acetone)

29
Q

What stereochemistry needs to be considered for WES?

A

Sn2 rules

  • inversion if carbon w/ LG is stereocenter
  • NO RXN on sp2 carbon w/ LG
  • no stereochem change at a-carbon of alcohol
30
Q

Is the hydroxyl group of an alcohol a good leaving group?

A

No, the LG would be -OH which is a strong base! Good leaving groups are weak bases

31
Q

What must happen for an alcohol to participate in substitution?

A

conversion of OH to a good leaving group by protonating OH to become H2O

32
Q

What is required for alcohol protonation?

A

strong acid such as HCl or H2SO4

33
Q

Do ethers and epoxides have a good LG?

A

No, neither, but epoxides are so strained reactions are favorable to open the ring and reduce strain

34
Q

What is a intramolecular WES of halohydrins?

A

A halohydrin reacts with NaH to form an epoxide . (One molecule reacts with itself essentially)

35
Q

What is the mechanism of intramolecular WES epoxide synthesis?

A

1) acid-base reaction btw alcohol and NaH
2) Sn2 reaction w/ itself
* note that Sn2 backside-attack requires anti-periplanar configuration btw hydroxyl and LG

36
Q

What type of conformation does WES epoxide synthesis require for the halohydrin to react?

A

anti-periplanar, may need a 180º rotation

this is required for Sn2 backside attack

37
Q

What is the base/nuc/electrophile in WES epoxide synthesis?

A

base = NaH (deprotonation to make alkoxide)
nuc = alkoxide (1º, 2º, 3º)
elect = 1º or 2º alkyl halide (on same molecule, or tosylate)
** no sp2C-LG

38
Q

What type of solvent is needed for intramolecular WES epoxide synthesis?

A

polar aprotic (DMSO, MeCN, THF, DMF, acetone)

39
Q

What are the stereochemical considerations for WES epoxide synthesis?

A

must be anti-pp to react for Sn2 backside attack!

40
Q

What are dehydration reactions of alcohols?

A

removal of H2O from an alcohol in the presence of a strong acid to form an alkene

41
Q

What types of alcohols (subst.-wise) are most likely to react/dehydrate?

A

more substituted alcohols (3º)

42
Q

What happens in an alcohol dehydration alkene synthesis reaction?

A

an alcohol reacts with tosic acid (TsOH) or sulfuric acid to make an alkene

43
Q

What is the mechanism for alcohol dehyd alkene synth?

A

2º and 3º = protonation + E1

1º = protonation + E2

44
Q

How is dehydration catalyzed?

A

acid-catalyzed

45
Q

What is acid/alcohol of alcohol dehyd alkene synthesis?

A 
acid = must have non-nucleophilic conj. base (otherwise could cause Sn1 to compete)
alcohol = carbon must be sp3
46
Q

What is the solvent for alcohol dehyd alkene synth?

A

acid is the solvent

47
Q

What are the stereochemical considerations for alcohol dehyd alkene synth?

A

alpha carbon is irrelevant and trans-alkene are major

48
Q

In which reactions can carbocation rearrangement occur?

A

alcohol dehydration alkene synthesis

49
Q

What are regioisomers?

A

constitutional isomers arising from a common starting material or intermediate

50
Q

What is the goal of carbocation RAR?

A

carbocation stability

51
Q

What is a 1,2-hydride shift? When does it occur?

A

carbocation RAR where 2º carbocation shifts to adjacent carbon that is 3º before proceeding with reaction to stabilize carbocation
*can occur any time there is a 2º carbocation!

Organic Chemistry (26 decks)

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