Hydrocarbons, Alcohols, and Substitutions Flashcards

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1
Q

methyl, primary, secondary, tertiary, qaternary carbons on alkanes

A

methyl - bonded to chain with no other carbons
primary - bonded to one other carbon/bonded to the chain and one other carbon
secondary - 2…
tertiary - 3…

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2
Q

boiling point properties of alkanes

A

increase as carbons added - molecular weight and intermolecular forces increase
branching lowers boiling point

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3
Q

melting point properties of alkanes

A

increases with increasing molecular weight

branching increases melting point

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4
Q

density of alkanes

A

lowest density of all groups

density increases with molecular weight

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5
Q

alkane solubility

A

almost totally insoluble in water
soluble in benzene, carbon tetrachloride, chloroform, and other hydrocarbons
if alkane contains polar functional group, polarity and solubility of molecules decreases as carbon chain is lengthened

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6
Q

alkanes of four carbons or less are ___ at room temp

A

gases

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7
Q

ring strain is zero for….

A

cyclohexane, increases as rings become larger and smaller

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8
Q

the ___ conformer of cyclohexane predominates

A

chair - lowest energy

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9
Q

equatorial hydrogens

A

hydrogens projecting outward from the center of the ring

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10
Q

axial hydrogens

A

projecting upward or downward in ring

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11
Q

when ring reverses its conformation, all the hydrogens….

A

reverse their orientation (equatorial axial)

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12
Q

large substituents in axial position…

A

crowding occurs, raises energy level –> less stable

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13
Q

combustion

A

when alkanes are mixed with oxygen and energy is added
high temps (inside flame)
radical reaction
CH4 + 2O2 –> CO2 + 2H2O +heat

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14
Q

heat of combustion

A

change in enthalpy of a combustion reaction

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15
Q

the higher the heat of combustion, the higher the…

A

higher the energy level of the molecule, less stable

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16
Q

Alkanes will react with halogens in the presence of heat or light to form a ___ ___

A

free radical: highly reactive species with unpaired e-

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17
Q

halogenation

A
  1. initiation: halogen starts as diatomic molecule, homolytically cleaved by heat or light –> 2 free radicals
  2. propagation: halogen radical removes H from the alkane –> alkyl radical. alkyl radical reacts with diatomic halogen –> alkyl halide and new halogen radical
  3. termination: 2 radicals bond or a radical bonds to the wall of the container to end the chain reaction or propagation
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18
Q

reactivity of halogens from most reactive to least

A

F, Cl, Br, I

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19
Q

___ are more acidic than ____

A

alkenes are more acidic than alkanes

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20
Q

the more highly substituted the alkene, the more ____

A

the more thermodynamically stable

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21
Q

elimination reaction –>

A

alkene

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22
Q

dehydration of an alcohol

A

E1 reaction, alcohol forms an alkene in presence of hot concentrated acid

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23
Q

E1

A

rate depends upon concentration of only 1 species

carbocations

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24
Q

carbocation stability

A

most: tertirary, secondary, primary, methyl : least

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25
Q

Saytzeff rule

A

the major product of elimination will be the most substituted alkene

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26
Q

dehydrohalogenation

A

E1 (absence of strong base) or E2 (high concentration of strong bulky base)

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27
Q

E2 dehydroghalogenation

A

1 step

base removes a proton from the carbon next to the halogen containing carbon, halogen drops off leaving alkene

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28
Q

nucleophile

A

electron rich compound, donate an e pair to form covalent bond

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29
Q

syn addition

A

same side addition

in catalytic hydrogenation

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30
Q

electrophilic addition

A

important reaction for alkenes

1: H of hydrogen halide acts as electrophile, adds to doulbe bond via Markvonikov’s rule. rate determining slow step
2. new carbocation picks up negatively charged halide ion

31
Q

electrophile

A

electron loving species, at least partial positive charge

32
Q

double bond of alkene will attract ….

A

electrophiles, is an e- rich environment

33
Q

Markovnikov’s rule

A

the hydrogen will add to the least substituted carbon of the double bond
-when hydrogen halides are added to alkenes, in electrophilic addition reactions

34
Q

anti-Markovnikov addition

A

is peroxides are present, the bromine (not the H) will add to the least substituted carbon

35
Q

hydration of an alkene

A

water added to an alkene in presence of acid, follow Markovnikov’s rule, low temps and dilute acid –> alcohols

36
Q

anti-addition

A

addition from opposite sides of double bond

37
Q

halogenation of an alkene

A

add one to each C of double bond

38
Q

benzene only undergoes ___ reactions

A

substitution, not addition

39
Q

benzene is a ____ molecule stabilized by ____

A

flat molecule stabilized by resonance

40
Q

if benzene has one substituent, remains 5 positions labeled….

A

ortho (2 closest) , meta (next 2), para (1)

41
Q

SN1 reaction

A

2 steps

  1. formation of carbocation, slow rate determining step, leaving group leaves
  2. nucleophile attacks he carbocation
42
Q

the rate determining step of SN1 is independent of of the concentration of the ____ and is directly proportional to the concentration of the ____

A

independent of nucleophile, proportional to concentration of substrate (elecrophile or molecule being attacked by the nucelophile)

43
Q

SN2 reactions

A

1 step, rate dependent on concentration of nucleophile and substrate
nucleophile attacks substrate from behind leaving group, knocks leaving group free while bonding to the substrate

44
Q

inversion of configuration for SN2

A

inversion of configuration on the carbon being attacked by the nucleophile

45
Q

SN2 reactions don’t typically occur with ____ substrates

A

tertiary substrates, tertiary carbon would sterically hinder the nucleophile

46
Q

nucleophile SN1 vs. SN2

A

SN2 requires a strong nucleophile, nucleophile strength doesn’t affect SN1

47
Q

Substrate for SN1 vs. SN2

A

SN1: secondary or tertiary substrate
SN2: methyl, primary, or secondary; don’t occur w/ sterically hindered substrates

48
Q

solvent for SN1 vs. SN2

A

highly polar solvent increases rate of SN1 by stabilizing carbocation, slows SN2 by stabilizing nucleophile

49
Q

speed of SN1 vs. SN2

A

speed of SN2 depends on concentration of substrate and nucleophile, speed of SN1 depends on concentration of just substrate

50
Q

stereochemistry of SN1 vs. SN2

A

SN2 inverts stereochemistry about chiral center, SN1 creates racemic mixture

51
Q

carbon skeleton rearrangement SN1 vs. SN2

A

SN1 may rearrange, SN2 never rearranges carbon skeleton

52
Q

elimination occurs when the nucleophile behaves….

A

as a base rather than a nucleophile : abstracts proton rather than attacking carbon

53
Q

alcohols follow same trend as alkanes, but boiling and melting points are higher due to ____

A

hydrogen bonding - increases the intermolecular forces which must be overcome to change phase

54
Q

alcohols are much _____ soluble in water than alkanes and alkenes

A

alcohols are much more soluble in water - hydroxyl group increases polarity
longer the carbon chain, the less soluble

55
Q

order of acidity of alcohols

A

strongest : methyl, primary, secondary, tertiary : weakest

56
Q

Grignard Synthesis of an alcohol

A

with organometallic compound, C attacks C with double bonded O, O accepts H

57
Q

Grignard reagents will react with ______ and can deprotonate ____

A

react with: C=N , C=-N, S=O, N=O

deprotonate: O-H, N-H, S-H, C=-C-H

58
Q

alcohols like to act as….

A

nucleophiles, nucleophilic addition or substitution

59
Q

___ and ___ alcohols can be oxidized

A

primary and secondary alcohols

60
Q

oxidation:

A

loss of H2, addition of O or O2, addition of X2 (halogen)

61
Q

reduction

A

additions of H2 or H-, loss of O or O2, loss of X2

62
Q

neither oxidation or reduction

A

additions or loss of H+, H2O, HX

63
Q

oxidizing agents will have lots of ____

A

oxygen

64
Q

reducing agents will have lots of ___

A

hydrogen

65
Q

formation of alkyl halide from alcohol

A

OH group attackes H from HX –> water

X- attacks C and water leaves

66
Q

alcohols form esters called

A

sulfonates: very weak bases and excellent leaving groups, used to protect alcohols

67
Q

formation of sulfonates

A

nuceleophilic substitution, alcohol acts as nucleophile, retention of configuration

68
Q

tosylates and mesylats

A

commonly used sulfonates

69
Q

pinacol rearrangement

A

dehydration of an alcohol that results in an unexpected product, ultimately forms pinacolone and regenerated acid catalyst

70
Q

____ and relativerly non-reactive

A

ethers

71
Q

___ is almost always the anser to sollvent questions

A

Ether - relatively low boiling point, roughly as soluble in water as alcohols, organic compounds tend to be more soluble in ethers because no H bonds need to be broken

72
Q

ethers are cleaved by….

A

cleaved by HI and HBr to form alcohol and alkyl halide

R-O-R + HBr –> ROH + RBr

73
Q

epoxides

A

three membered cyclic ethers

react with water in presence of acid to from diols called glycols with anit-addition