Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Organic Chemistry > Ch. 10 - Alkenes & Addition Reactions (Week 2, Quiz 2) > Flashcards

Ch. 10 - Alkenes & Addition Reactions (Week 2, Quiz 2) Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Chemistry flashcards Periodic Table flashcards Chemistry 101 flashcards Organic Chemistry 101 flashcards
1
Q

What are alkenes?

A

compounds that contain C-C double bonds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are terminal alkenes?

A

have a double bond at the end of the carbon chain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are internal alkene?

A

have a least one C atom bonded to each end of double bond

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are cycloalkenes?

A

have double bond in the ring

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What makes up a double bond?

A

one pi bond and one sigma bond

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is hybridization, geometry and angles of pi bond carbons?

A

sp2, trig planar, 120º

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Which is weaker: sigma or pi bond?

A

pi bond is weaker, easier to break so alkenes go under many reactions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Why do pi bonds go under many reactions?

A

have pi bond that is easy to break

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

T/F: Double bonds have free rotation.

A

False, double bonds have restricted rotation. For rotation to occur, double bond would have to break

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is stereoisomerism of double bond?

A

when 2 groups on each C=C end are different, two diasteriomers are possible

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the two diastereomers possible for a carbon double bond with stereoisomerism? Which is mores stable?

A

cis and trans; trans is more stable

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the formula for an acyclic alkene?

A

CnH2n

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Why are alkenes considered unsaturated?

A

they have less than the max number of hydrogens per carbon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the max number of hydrogens a carbon chain can have?

A

2n+2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How are alkenes named?

A

1) name longest C chain with both carbons of double bond and change -ane to -ene
2) number the chain giving the double bond the lower number

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are dienes?

A

two double bonds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are trienes?

A

three double bonds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are alkenols?

A

have both a double bond and a hydroxyl group

ex. prop-2-en-1-ol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How are cycloalkenes named?

A

give double bond carbons numbers 1 and 2 and then give lowest number to subs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What types of IMFs do most alkenes have?

A

just weak van der Waals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What are MP/BP and solubility properties of alkenes?

A

low MP/BP that increases and number of carbons/surface area increases
soluble in organic solvents but not in H2O

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Why do cis and trans alkenes have slightly different properties?

A

sp3 hybridized alkyl carbon donates electron density to sp2 hybridized alkenol carbon which creates a slight polar bond

in a cis isomer, dipole moments are reinforced so there is a net dipole

in trans isomer, dipole moments cancel so there is no net dipole

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What are the three ways so far that alkenes can be prepared?

A

1) dehydrohalogenation of alkyl halides with a strong base (E2)
2) acid-catalyzed dehydration of alcohols with H2SO4 or TsOH (E1/E2)
3) dehydration of alcohols with POCl3 and pyridine (E2)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What occurs in a general addition reaction?

A

a pi bond breaks and 2 new sigma bonds form

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

T/F: alkenes are electron poor

A

false, they are electron rich

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What do simple alkenes react with (general)?

A

electrophiles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What are SM and P of hydrohalogenation?

A 
SM = alkene
P = alkyl halide
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What are reactants of hydrohalogenation?

A

H-X (X = Cl, Br, I)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What is the mechanism of hydrohalogenation?

A

addition (Sn1)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What are the major steps of alkene hydrohalogenation?

A

an alkene double bond electrons bind to H and HX bond breaks giving electrons to X (forms carbocation)

nucleophilic X- attacks carbocation via Sn1 to make alkyl halide

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Which is the RDS and fast steps of hydrohalogenation? Aka which step has the highest activation energy?

A 
RDS = formation of carbocation (breaking pi bond) *has higher activation energy*
fast = Sn1 to make alkyl halide
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Which hydrohalogenation transition state has highest energy?

A

state between alkene and carbocation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What could the two reactions for hydrohalogenation be classified as in terms of acids/bases?

A

Lewis A-B reaction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Why are addition reactions exothermic?

A

sigma bonds formed are stronger than the pi bonds broken

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What is Markovnikov’s rule?

A

in addition of HX to unsymmetrical alkene, the H atoms binds to the LESS sub’d carbon to give a MORE sub’d carbocation (the most stable carbocation will form)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

What configurations will be given when an electrophile attacks a carbocation and the carbon becomes a stereocenter?

A

both configurations will be giving (R and S); will form a racemic mixture

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Does Markovnikov’s rule see the future?

A

No, so carbocations can’t know if they will be able to undergo a methyl or hydride shift, therefore, even if one can and the other can’t, they will both form because molecules can see the future!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

Can Mark’s rule see resonance?

A

Yes! A carbocation wants to be closer to double bonds so it can be resonantly stabilized. So the carbocation with resonance stabilization will form and the other won’t.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

What explains Marl’s rule? (another rule)

A

Hammond’s Postulate

  • for an endothermic reaction, the transition state is closer in structure and energy to the product
  • what stabilizes the product will stabilize the transition state
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

What is the name for a mixture of diastereomers?

A

scalemic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

If a molecule that already has a stereocenter undergoes alkene addition with HX and the alpha carbon will become a stereocenter, what will the products be?

A

diastereomers!

42
Q

For naming alkenes, are the numbers of both carbons of the alkene added to the name?

A

no, only the first carbon (lower number)

43
Q

Why do enantiomers form for alkene hydrohalogenation (HX addition)?

A

because addition occurs from top and bottom of planar double bond

44
Q

Do syn or anti products form for alkene + HX = alkyl halide?

A

both syn and anti

45
Q

What makes HX addition regioselective?

A

Mark’s rule (H bonds to less sub’d carbon to give more sub’d carbocation)

46
Q

What is the RDS for HX addition?

A

formation of carbocation

47
Q

What are SM and P of acid-catalyzed alkene hydration?

A 
SM = alkene
P = alcohol
48
Q

What are reagents for acid-catalyzed alkene hydration?

A

water and acid (H2SO4 or TsOH)

49
Q

What is mechanism for acid-catalyzed alkene hydration?

A

Addition, Sn1

50
Q

What are major steps of acid-catalyzed alkene hydration?

A

alkene is protonated by acid (H goes to less sub’s carbon) … Mark’s rule… forms carbocation

nuc attack by water on carbocation via Sn2 forms more sub’d alcohol

51
Q

What is the solvent of acid-catalyzed alkene hydration?

A

water

52
Q

Can RAR occur for acid-catalyzed alkene hydration?

A

Yes, proceeds by Sn1 so carbocation

53
Q

Can alkene reactions occur on aromatic rings?

A

No ma’am

54
Q

What type of products (stereochemistry) does acid-catalyzed alkene hydration form?

A

if st, center results, then racemic mixture

55
Q

What type of addition products (syn or anti) does acid-catalyzed alkene hydration form?

A

both syn and anti

56
Q

Why is acid-catalyzed alkene hydration considered “acid-catalyzed/”

A

because reaction regenerates acid

57
Q

What are three consequences of carbocation intermediates?

A

1) H adds to less sub’d carbon to form more stable carbocation (mark)
2) addition occurs in syn + anti
3) RAR can occur

58
Q

How many times does water react in acid-catalyzed alkene hydration?

A

twice

59
Q

What are SM and P of acid-catalyzed alkene hydroalkoxylation?

A 
SM = alkene
P = ether
60
Q

What are reagents of acid-catalyzed alkene hydroalkoxylation?

A

acid (H2SO4 or TsOH) and ROH

61
Q

What is mechanism of acid-catalyzed alkene hydroalkoxylation?

A

Sn1

62
Q

What are major steps of acid-catalyzed alkene hydroalkoxylation?

A

alkene is protonated with acid and carbocation forms following Mark’s rule

nuc attack by ROH oxygen on carbocation gives alcohol via Sn1

63
Q

What is the solvent of acid-catalyzed alkene hydroalkoxylation?

A

alcohol

64
Q

What type of products are formed (stereochemistry) by acid-catalyzed alkene hydroalkoxylation?

A

racemic

65
Q

Does syn or anti occur for acid-catalyzed alkene hydroalkoxylation?

A

both syn and anti products (racemic mixture of each)

66
Q

What makes acid-catalyzed alkene hydroalkoxylation regioselective?

A

follows Mark’s rule

67
Q

Can RAR occur for acid-catalyzed alkene hydroalkoxylation?

A

Yes, Sn1

68
Q

What reactions is acid-catalyzed alkene hydroalkoxylation exactly like?

A

acid-catalyzed alkene hydration (making an alcohol from an alkene)

69
Q

What causes X2 to be momentarily polar?

A

momentary dipole is formed when electron cloud of Br2 oscillates

70
Q

What are SM and P of alkene dihalogenation?

A 
SM = alkene
P = vicinal dihalide
71
Q

What are reagents of alkene dihalogenation?

A

X2 where X = Cl or Br only

72
Q

Why can’t F or I react in alkene dihalogenation?

A

F is too reactive and I is too reversible

73
Q

What is mechanism for alkene dihalogenation?

A

anti addition, Sn2

74
Q

What are major steps for alkene dihalogenation?

A

pi bond electrons go to Br and same Br bonds to other side of pi bond to make bridged halonium ion

other Br- attackes MORE sub’d carbon (the carbon that can better handle partial positive charge) and then becomes vicinal halide via Sn2

75
Q

Can alkene dihalogenation undergo RAR?

A

No, Sn2 so no carbocation forms

76
Q

What type of addition is X2?

A

anti only

77
Q

What are stereochemical considerations of alkene dihalogenation?

A

anti product is made exclusively

two bridged halonium ions form (one with dashes and one with wedges) so racemic products form after backside attack

cis and trans alkene isomers each give racemic mixture which are diastereomers of eachother

78
Q

Why is alkene dihalogenation considered stereospecific?

A

one stereoisomer forms (anti not syn) note: still racemic!

79
Q

What is the difference between stereoselective and stereospecifc?

A

stereoselective is when one stereoisomer forms (anti or syn) and stereospecific is when two or more stereoisomers form but one is major/minor

80
Q

Why is the more sub’d carbon attacked on the holonium ion of alkene dihalogenation?

A

because it better holds positive charge

81
Q

What are SM and P of alkene halohydration?

A 
SM = alkene
P = halohydrin
82
Q

What is a halohydrin?

A

has an alcohol group and X group on adjacent carbons

83
Q

What are reagents of alkene halohydration?

A

X2 (X=Cl,Br,I) and water

84
Q

What is mechanism of alkene halohydration?

A

anti addition, Sn2

85
Q

What are major steps of alkene halohydration?

A

an alkene reacts with X2 to form bridged halonium ion (x2)

Water attacks the carbon where partial charge would be most stable to open ring

Water depronates H2O to make alcohol group

86
Q

Does alkene halohydration undergo RAR?

A

No, Sn2 so no carbocation

87
Q

What is the solvent of alkene halohydration?

A

water

88
Q

What type of addition is alkene halohydration?

A

anti addition only

89
Q

What are the stereochemical considerations for alkene halohydration?

A

always anti addition

2 bridged halonium ions form so both anti trans products form

cis and trans alkenes make racemic mixtures that are diastereomeric of eachother

90
Q

Why does water act as nuc and not X- in alkene halohydration?

A

Because water is in much greater concentration (1000000:1)

91
Q

With what other reagents can alkene halohydration occur?

A

NBS (just a source of Br2)

DMSOm H2O

92
Q

Why is alkene halohydration regioslective?

A

water attacks the more sub’s carbon to deal with partial positive charge

93
Q

What are SM and P of brown alkene hydroboration-oxidation?

A 
SM = alkene
P = anti-mark. alcohol
94
Q

What are reagents of brown alkene hydroboration-oxidation??

A

BH3 and H2O2, NaOH

95
Q

Where does alcohol end up for brown alkene hydroboration-oxidation?

A

on the LESS sub’d carbon

96
Q

Are there carbocations in brown alkene hydroboration-oxidation?

A

No

97
Q

Why is borane electrophilic?

A

it has an empty p-orbital

98
Q

Where does BH2 end up in hydroboration?

A

less sub’s carbon (like alcohol)

99
Q

What kind of addition is brown alkene hydroboration-oxidation?

A

always syn addition, forms racemic mixture

100
Q

What am I going to tell you to do?

A

Stay calm, have fun, enjoy the moment and be proud

Organic Chemistry (26 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions