Unit 3 Flashcards
1
Q
syn addition rxs
A
both atoms add to the same side of the ring to form a cis product
2
Q
if a syn reaction occurs with a compound that is chiral, what is the product
A
the product formed from the above and below reactions will form, and they may be diasteromers or enantiomers
3
Q
concerted mechanism
A
when all of the bond breaking and forming occurs without the formation of an intermediate
4
Q
anti addition
A
groups are added to the opposite side of ring to form a trans product
5
Q
what kind of mechanisms are used in syn reactions
A
concerted
6
Q
what kind of mechanisms are used in anti reactions
A
step wise
7
Q
step wise mechanism
A
the addition occurs in a step wise manner with the formation of an intermediate
8
Q
what a makes halogens effective electrophiles
A
they are nonpolar but highly polarizable
9
Q
what types of atoms make the best leaving groups
A
stable ions
10
Q
what types of reagents and solvents are needed for a halogenation reaction
A
the reagent must be Cl2 or Br2
the solvent must be a nonnucleophile
11
Q
why must the solvent in a halogenation reation be a non-nucleophile
A
because a nucleophillic solvent would compete with the reagents and react with Cl or Br
12
Q
what type of mechanism is halogenaton
A
2 step mechanism
13
Q
what are the two step to a halogenation reaction
A
1) the electrons of the alkene pi bond flow into the first halogen, pushing the H atoms to one side and creating a partial carbocation and an halide ion
2) the free floating halide attaches to the partial carbocation on the opposite side of the ring
14
Q
why doesn’t the halogen reaction not fully form a carbocation
A
because as the carbon becomes electron deficient the electrons from the halogen form a sigma bond
15
Q
bronsted acid
A
a proton donor (H3O)
16
Q
bronsted base
A
a proton acceptor (OH)
17
Q
neutral acids form
A
negative CB
18
Q
positive acids form
A
neutral CB
19
Q
negative bases form
A
neutral CA
20
Q
neutral bases from
A
positive CAs
21
Q
what type of reaction mechanism is used in an acid base reaction
A
concerted
22
Q
how is the strength of an acid determined
A
how many other molecules will a molecule force a proton on to
23
Q
how does pKa relate to the strength of an acid
A
a lower pKa means a stronger acid
24
Q
how strong will the conjugate base of a weak acid be? why?
A
it will be strong, because the acid will not be likely to give up protons but will easily accept them
25
how strong will the conjugate base of a strong acid be
it will be weak, because the acid will be very liked to give up protons and not easily accept them
26
if given an acid reaction, what is used to determine what direction the reaction will go? why?
the reaction will favor the stronger acid, because a stronger acid will create a weaker base with a strong negative charge
27
what are the 4 factors that influence the stability of a negative charge (ARIO)
1) type of atom
2) resonance
3) induction
4) orbitals
28
how does the type of atom influence stability of a negative charge
larger, more electronegive atoms are better at stabilizing a negative charge
29
what is characteristic of an atom is more important in stabilizing negative change, size or electronegativity (example)
size (S stabilizes better than oxygen)
30
how does resonance stabilize negative charge
by spreading the charge over several atoms
31
induction
the attraction of negative charges to more electronegative atomes
32
how does induction stabilize negative charge
it spreads charge out like resonance
33
what are two factors influencing induction (examples)
1) electronegativity (F is more inductive than Cl)
| 2) distance (induction can only cross 3 bonds)how a
34
how do orbitals influence the stability of a negative charge
sp orbitals pull electrons closer to the nucleus and stabilze the charge
35
hoow are oribitals ranking according to their ability to stabilize negative charge
sp > sp2 > sp3
36
counter ion
spectator ion
37
if LiH is in a problem, what is happening
the LiH will dissociate into Li+ and H-, and the Li will find another atom to attach to
38
what is the leveling effect
the strongest base in the reaction will always take the most acidic proton from the strongest acid
39
T/F a conjugate acid stronger than the solvent in the reaction can't exist
true, any acid stronger than the conjugate acid of your solvent will donate protons to the solvent
40
in a reaction where the desired product is a base, what is important to remember
the solvent can't form a more basic molecule than the desired base because the product will take protons from the solvent and not form
41
in a reaction where the desired product is an acid, what is important to remem ber
the solvent can't form a stronger conjugate acid than the product or the product will give its protons to the solvent and not form
42
lewis acids
electron acceptor
43
lewis bases
electron donor
44
what are three examples of lewis acids that arent bronsted acids
AlR3, BrR3, CR3+
45
what do all the common lewis acids that are bronsted acids have in common
Al and Br are stable with three electrons
carbocation is an intermediate
46
what are the 6 steps for naming an alkene
1) the parent chain must include both C=C carbons
2) identify and name all the substituents
3) number the parent chain so the alkene has the lowest number
4) number the substituents
5) list the number substituents in alphabetical order
6) end the parent chain with -ene
47
what happens when the longest chain of an alkene doesn;'t include the whole alkene
the shorter chain that does include the alkene is used
48
what are dienes and how are they named
molecules with two alkenes
-adiene
49
T/F the parent chain of a diene includes both alkene bonds
true
50
can the bonds on an alkene rotate?
no
51
how many isomers are possible in cyclic alkenes with less than 8 carbons
1, only cis alkenes are possible with less than 8 carbons
52
T/F if one of the carbons of an alkene has identical groups there is no stereoisomer of that alkene
true
53
what is the E/Z designation used for
it takes the place of cis and trans when there are different groups on each carbon
54
what does Z stand for
a cis configuration in an alkene with four different groups
55
what does E stand for
a trans configuration in an alkene with four different groups
56
when are cis and trans used to designate alkenes
when the two carbons have identical groups
57
nucleophiles
atoms or molecules that are attracted to positive charges
58
electrophiles
atoms or molecules that are attracted to negative charges
59
T/F the conjugate bases of most acids function as electrophiles
false, they function as nucleophiles
60
T/F nucleophiles/electrophiles will never react with molecules of the same type
true
61
what is needed for a carbon atom to produce a nucleophile
a pi bond or a nonbonding pair
62
what are two functions of the leaving group
- it removes electron density from a carbon to make it electrophilic
- it is able to stabilize a negative charge after it is expelled
63
what is needed for oxygen to be nucleophilic
a pi bond, a nonbonding pair, or a OH bond
64
can a neutral oxygen be nucleophilic
yes
65
what is more nucleophilic, an anion or a neutral atom
the anion (S-, O-)
66
what is needed for sulfur to be nucleophillic
a nonbonding pair, a pi bond, or an SH bond
67
what are 9 common electrophiles
1) carbocations
2) ketones
3) aldehydes
4) esters
5) amides
6) halogens
7) expoxides
8) alkyl halides
9) acids)
68
T/F electrophiles will interact with other electrophiles
false
69
why are halogens considered be electrophiles
because they can flucuate in electron arrangement rapidly and attract electrons from a nucleophile
70
when deciding a nucleophile and electrophile will react what are two considerations
1) weak bonds break easier than strong bonds
| 2) a strong base will displace a weak base
71
why can the electrons from pi bonds flow into electrophiles more easily than those from sigma bonds
because of the orientation of the p orbital the electrons are not found between the nuclei
72
why can alkenes act as bases and nucleophiles
because the pi bond of an alkene acts like a less active nonbonding pair
73
what type of reaction is common with alkenes
addition reactions
74
what are three types of addition reactions
1) cation forming reactions
2) syn-addition reactions
3) anti-addition reactions
75
three types of addition reactions that require an acid
1) hydrohalogenation
2) hydration
3) hydroalkoxyation
76
what is the process of hydrohalogenation
a binary acid added to an alkene forms an alkyl halide as one C gets an H and one C gets an X
77
racemic mixture
when two possible stereoisomers are present in equal amounts
78
what is the process of hydration
H2O added to an alkene produces alcohol
79
markinovs rule
in an addition reaction the carbon with the most hydrogens will get the hydrogen
80
why dont alkenes react with H2O
they are both nucleophiles
81
what will make an alkene react with water
any amount of an acid to form H3O and act as a catalyst
82
what is a solvent typically used in hydration reactions
a polar organic solvent that will produce a homogenous mixture with water (dimethylsulfoxide)
83
what happens in a regioselective reaction
one of the possible products is formed more often than the others
84
what is the effect of substitution on alkene reactions
the more carbons an alkene has attached the faster it will react
85
T/F the halogen in a hydrohalogenation reaction will always end up on one of the alkene carbons
false
86
what are two types of carbocation rearrangement
- hydride shift
| - methyl shift
87
hydride shift
the movement of an H to another adjacent carbon
88
methyl shift
the movement of a CH3 group to an adjacent carbon
89
what determines if a methyl or hydride shift can happen
- they will only happen to gain more resonance stabilization
| - they will only shift if the recipient of the positive charge is the atom with the most C-C bonds
90
can a CH2+ ion carbocation do a hydride or methyl shift with a CC2H carbon?
yes, because the CC2H carbon is more able to hold positive charge
91
how is deutritum used in determining reaction mechanisms
deutritium is used instead of regular hydrogen
92
deuterium
a hydrogen atom with one proton and one neutron
93
what is the stepwise mechanism for a hydration reaction
1) H3O donates a proton to one of the alkene carbons
2) H2O forms oxonium with the carbocation formed
3) the positive oxonium donates an electron H2O to reform H3O
4) the result is an alcohol
94
what makes carbocation rearrangement possible in a reaction
the formation of a carbocation
95
why are carbocation rearrangements problematic for organic reactions with a specific end result
they are very fast and unstoppable, so H-X reactions are only useful when rearragements won't occur
96
what is meant by the "least" substituted carbon
the least substituted carbon is the carbon with the fewest C-C bonds
97
why do the H goto the carbon with the most H's in markinovs rule
because the carbon with the most H's would form the less stable carbocation if it didn't get H
98
what will be the result of a hydrogenation reaction
the syn additition of two hydrogens
99
when will any syn addition reaction produce enantiomers
when the molecule added onto is chiral
100
what is syn dihydroxylation?
what are the catalysts used
the syn addition of two OH groups to an alkene
OsO4, KMno4
101
what is the result of dihyrdroxylation
the syn addition of two OH groups producing a vicinal diol
102
vicinal diol
a molecule with an OH group on adjacent carbons
103
what are the two steps of a dihydroxylation reaction
1) the oxygens of OsO4 or KMnO4 are added simultaneously to the alkene carbons
2) the 2nd reactant breaks the rest of the molecule away to leave only the OHs
104
what are the two steps of a dihydroxylation reaction
1) the oxygens of OsO4 or KMnO4 are added simultaneously to the alkene carbons
2) the 2nd reactant breaks the rest of the molecule away to leave only the OHs
105
What is hydroboration/Oxidation
the process by which an OH group is added to the most substituted carbon (with the most C bonds) and an H to the least substituted carbon
106
why is hydroboration special
because it is the only reaction we learn about that added hydrogens in an anti-markovnikov fashion
107
what is the process of hydroboration
1) BH3 attaches it BH2 to the carbon with the most hydrogens, the H attaches to the C with the least hydrogens
2) BH2 is cleaved off by a second reactant to leave an OH behind
108
what are there reactants in hydroboration/oxidation
- Borane (BH3)
- KOH
- H2O2
109
what is THF
an additive in a hydroboration reaction that helps stabilize borane
110
when would the H's on a CH2 not be equivalent on NMR
when the CH2 is adjacent to a chirality center
111
what is oxymercuriation
what are the reagents used
- the anti addition of an OH and H without carbocation rearragement through a Hg cyclic intermediate
- Hg(OAc)2, NaBH4
112
what will a reaction with MCPBA produce
an epoxide from an alkene
