Reactive Intermediates

Question 1

Carbocation

Answer 1

Is a positive ion in which a positive charge resides on the carbon atom

Question 2

Carbocation stability

Answer 2

Tertiary are most stable,

Pi systems adjacent to carbocation also stabilize via resonance

Question 3

Carbocation rearrangement

Answer 3

Often occurs during Sn1 & E1 reactions

Question 4

1,2 shift/ Wagner-Meerwein transposition

Answer 4

When a carbocation rearranges into a more stable tertiary carbocation

Question 5

Carbanion

Answer 5

An ion in which a carbon atom has a -1 charge, often formed by heterolytic cleavage between carbon & a metal

Question 6

Carbanion

Answer 6

Conjugate bases of hydrocarbons

Question 7

Free radical

Answer 7

A neutral species that contains an impaired electron

Question 8

Homolytic bond cleavage

Answer 8

He really form radicals, each fragment carries one electron from the broken bond

Question 9

Alkyl radical

Answer 9

Primary, secondary, tertiary; methyl radical = methyl cation

Question 10

Stability of free radical is associated with?

Answer 10

Their bond dissociation energies (BDE); the lower the BDE, the more stable the radical

Question 11

Prototypical free radical reaction for chlorination of methane

Answer 11

1. ) initiation
2. ) chain propagation
3. ) termination of propagation cycle

Question 12

Initiation

Answer 12

The dissociation of he radical precursor molecule and the formation of two free radicals under light or high temperature

Question 13

Chain propagation

Answer 13

The free radical abstract a hydrogen atom from the already; the the alkyl radical reacts with another precursor molecule

Question 14

Termination of the propagation cycle

Answer 14

Occurs when free radicals combine with one another

Question 15

Allylic

Answer 15

Carbon next to a C=C double bond; experiences enhanced free-radical reactivity

Question 16

Benzylic

Answer 16

Carbon next to a benzene ring; enhanced free radical reactivity

Question 17

Free radicals and carbocations are?

Answer 17

Both planar and sp2 hybridized

Question 18

Carbenes

Answer 18

Are neutral molecules of general formula R2C: in which a carbon atom has two sigma bonds and two electrons

Question 19

Benzynes

Answer 19

Compounds that are formed as reactive intermediates in the reaction of alkyl halides with strong bases (nuc aro sub)

Question 20

Enols

Answer 20

Compounds that exist as an equilibrium mixture of ketone and alcohol tautomers. Two forms are called the Keto form and Emil form

Question 21

Keto form vs enol form

Answer 21

Is more stable and predominates in simple ketones and aldehydes

Question 22

Organometallic compound

Answer 22

Consists of a carbon atom covalently bonded to a metal, carbon has a partial negative charge while meta has a partial positive charge

Question 23

Grignard reagents

Answer 23

Organomagnesium halides

Question 24

Preparation of Grignard reagent

Answer 24

Reaction between magnesium and alkyl halide (RX) in an ether solvent

Question 25

Most common grignard solvent

Answer 25

Diethylether; donates unshared electrons to the empty orbitals in magnesium, while ethyl groups solvated the alkyl fragments

Question 26

Grignard reagent most important reaction

Answer 26

Rxn with carbonyl compounds = forms tertiary alcohols

Question 27

Formaldehyde + RMgX

Answer 27

Primary alcohol (RCH2OH)

Question 28

Aldehyde (RCOH) + R’MgX

Answer 28

Secondary alcohol (RCHOHR’)

Question 29

Ketones (RCOR’) + R”MgX

Answer 29

Tertiary alcohol (RCOHR’R”)

Question 30

CO2 + RMgX

Answer 30

Carboxlyic acid (RCOOH)

Question 31

Organolithium reagents

Answer 31

More reactive than grignard reagents because Li is more electropositive than Mg

Question 32

Organolithium reagent preparation

Answer 32

Prepared by rxn with an alkyl halide (TX) and Group 1 metal an parotid solvent

Question 33

Organolithium reagent prep rxn

Answer 33

RX + 2M (Group 1) -> RM + M+X-

Question 34

Lithium Organocuprates

Answer 34

Useful in coupling 2 alkyl fragments to produce larger alkane

Question 35

Corey-House reaction

Answer 35

Rxn that uses lithium organocuprates to couple 2 alkyl fragments together

Question 36

Lithium dialkylcuprates (R2-Cu-Li)

Answer 36

Preferred organometallic reagent for Corey-House reaction

Question 37

Most commonly used lithium diaklylcuprates

Answer 37

Lithium dimethylcuprate (CH3)2 Cu-Li

Lithium divinylcuprate (H2C=CH)2 Cu-Li

Question 38

Dialkylcuprate prep

Answer 38

2RLi + CuX -> R2CuLi + LiX

Question 39

Organozinc reagents prep rxn

Answer 39

RX + Zn -ether-> RZnX

Question 40

Organozinc reagents reactivity

Answer 40

Not as reactive toward carbonyl compounds as RLi or RMg;

Question 41

Organozinc prep

Answer 41

often formed at rxn intermediates in reduction Rina b/w alkyl halides and zinc in acid media

Question 42

Simmons-Smith reaction

Answer 42

1. ) ICH2I + Zn -(ether/Cu)-> ICH2ZnI

2. ) formation of cylcopropane by reaction with alkene

Question 43

Oxymercuration rxn

Answer 43

Formed when Hg(O2CCH3)2 reacts with Alkenes in a mixture of H2O and THF

Question 44

Oxymercuration

Answer 44

Forms: beta-hydrocyalkylmercury(II) acetate

Question 45

Demercuration

Answer 45

Rxn that isolates oxymercuration product by treating it with sodium borohydride (NaBH4); yields an alcohol

Question 46

Solvomercuration-demercuration reaction

Answer 46

Like oxymercuration but used to synthesize ethers by subbing an alcohol for THF

Question 47

Benzenetricarbonyl chromium

Answer 47

Has three signs bonds b/w the CO groups and act and a benzene ring(not a phenyl group) attached to the metal act bonded to pi system

Question 48

Cyclobitadiene tricarbonyliron

Answer 48

Pi complex

Question 49

Ferrocene

Answer 49

Pi complex

Question 50

Pi complexes

Answer 50

System where a metal is bonded to the pi system of s benzene ring