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Flashcards in Analyzing Organic Reactions Deck (47):
1

Lewis Definition of Acids and Bases

concerns with the transfer of electrons in the formation of coordinate covalent bonds

2

Bronsted - Lowry Definition of Acid and Bases

focuses on proton transfer

3

Lewis Acid

electron acceptor in the covalent bond

tend to be electrophiles

vacant p-orbitals to accept electrons with or stay as positively polarized atoms

4

Lewis Base

electron donor for the covalent bond

nucleophiles

lone pair of electrons to donate or they just carry negative charge

5

Coordinate Covalent Bonds

when both electrons in the bond come from the same staring atom (the lewis base)

6

Bronsted Lowry Acid

species that donates a proton (loses positiveness)

7

Bronsted Lowry Base

species that accepts a proton (loses negativeness)

8

Amphoteric

molecules that can act as either Bronsted Lowry Acid/Base like water as it can accept and donate H+


Al(OH)3 HCO3- , HSO4-

9

Ka

acid dissociation constant

measures strength of an acid in solution

Ka = ( [H+] [A-] )/ [HA]

pka = - log Ka

10

More acidic molecules will have _____ pKa and more basic molecules will have ____ pKa

smaller , larger

11

Generally, bond strength ______ down the periodic table meaning that acidity ______ . Also the more electronegative an atom, the _____ the acidity.

When these two trends oppose each other, ______ takes precedence.

decreases

increases

higher

lower bond strength

12

Alpha Hydrogens

attatched to the alpha carbon of carbonyl carbons

they are the acidic hydrogen's easily lost as the -enol form of carbonyl carboanions are stabilized by resonance.

13

Functional Groups that act as acids are _______ . They are readily accepting lone pairs from ______ reactants

Functional groups that act as bases are ______.

Alcohols
Aldehyde/Ketone (alpha carbons)
Carboxylic Acids
Carboxylic Derivatives


basic (nucleophilic)

amines
amides

14

Nucelophiles

contain lone pairs/pi bonds that can from new bonds with electrophiles

good bases

15

Nucelophilic/Electrophilic strength is determined on _________ with a common electrophile. Thus they are a ______ property.

This is different from bases as acids/bases depend on _____ of a reaction, so it is a ______ property

relative rates of reaction

kinetic

equilibrium position

thermodynamic

16

Nucelophilicity is determined by 4 factors:

Charge: more electron density, the more nucleophilic it is

Electronegativity: decreases as electronegativity increases as they are less likely to share electron density

Steric Hindrance: bulkier molecules are less nucleophilic

Solvent: protic solvents can hinder nucleophilicity by protonating nucleophile or forming H bonds



17

In POLAR PROTIC solvents, nucleophilicity increases _____ the periodic table. In POLAR APROTIC solvents, nucleophilicity increases _______ the periodic table.

going down

going up

18

In protic solvents, nucleophilicity decreases in halogens like this:

In aprotic solvents, nucleophilicty decreases in this order:

I - > Br- > Cl - > F-

F > Cl > Br > I as no protons can get in the way and nucleophilicty depends on basicity


HI forms a strong acid so its less likely to form bonds with H

HF is a weak acid and will easily form bonds with H

19

Electrophiles

electron accepting species with a positive charge or polarized atom that will accept an electron pair

always act as acids

nature of leaving group influences electrophilicty of of species

20

A greater deal of positive charge increases electrophilicity, so a carbocation is _____ electrophilic than a carbonyl carbon.

more

21

Carboxlyic derivatives are ranked by electrophilicity from most reactive to least

Anhydrides, Carboxylic Acids, Esters, Amides

22

Leaving Groups

molecular fragments that retain electrons after heterolysis

23

Heterolytic Reactions

opposite of coordinate covalent bonds

a bond is broken and bothe electrons are given to one of the two products

best one stabilize the extra electrons

weak bases are more stable and make good leaving groups

can be augmented by resonance and inductive events

24

SN1 Reaction

1) the rate limiting step where leaving group leaves and a carbocation is made

2) Nucleophile then attacks the carbocation resulting in the substitution product


racemic mixture is made as it passes through a planar intermediate and the nucleophile can attack from either side

25

The more _____ the carbocation, the more _____ it is due to alkyl groups stabilizing the positive charge

substituted

stable

26

For SN1, the rte of the reation depends only on the concentration of the substrate

rate = k [R-L] where R-L is the thing that contains the leaving group

27

SN2 Reaction

1) nucleophile attacks the compound at the same time as the leaving group leaves

known as a concerted reaction (1 step)

nucelophile displaces the leaving group through a back side attack, thus the substrate cannot be sterically hindered. THEREFORE, the less subsituted carbon, the more reactive it is to SN2 reactions

there will be an inversion of the relative configuration

28

Rate of SN2 reaction determined by concentration of both the nucleophile and the original substrate

rate = k [Nu] [R-L]

29

When SN2 reaction occur, the position of subsituents around the carbon will be ____. an R will become an _____

inverted

S

30

Oxidation State

indicator of hypothetical chage an atom would have if all the bonds were completely ionic

31

Oxidation of Derivatives (most to least)

Carboxylic Acids > Aldehydes >Ketones > Imines > alcohols > alkl halides > amines

32

Oxidation

increase in oxidation state, lossing electrons or increasing number of bonds to oxygen and other hetero atoms (non C and H atoms)

33

Reduction

decrease in oxidation state, gain in electrons

increase in the number of bonds to hydrogen

34

Oxidation of Carbon

when bond betwe C - less electronegative atom is replaced by C - more electronegative atom (c's nitrogen, oxygen, halides)

35

Oxidizing Agent

is the element/compound which accepts the electron and
is reduced

good ones have high affinity for electrons or high oxidation states

36

Oxidation reactions tend to feature an ____ in the bonds to oxygen while oxidizing agents often contain ______ bonded to a large number of oxygen atoms.

increase

metals

37

Reduction of a Carbon

when a bond between a Carbon and an atom that is more electronegtaive gets replaced with Carbon with less electronegative atom

increasing bonds to hydrogen mostly

38

Good reducing agents

low electronegticities and ionization energies (sodium, magnesium, alumnimu, zinc)

or those with H- ion

39

Aldehydes and Ketones will be reduced to ____ and ____ alcohols respectively but slowly without a catalyst. (LiAlH4)

Amides can be reduced to amines using _______ which can also reduce carboxylic acids to _______ and esters to a pair of _____

primary and secondary

LiAlH4
primary alcohols

alcohols

40

Chemoselectivity

preferential reaction of one functional group in the presence of another functional group

41

A redox reagent will tend to act on the ______ priority fxnal group. Thus a molecule with alcohol/carboxylic acid will most likely react on a carboxylic acid than a alchol. This is because they have the _____ carbon.

More oxidized the carbon, the ____ electronegative groups around it and a more ____ charge for an electrophile to attack.

highest

most oxidized

more

positive

42

Priority of Functional Groups

Carboxylic Acids and Derivatives, Aldehyde/Ketone, Alcohol, Amine

43

Carbon of A Carbonyl

1) carbonyl carbon has positive charge due to electronegativity of oxygen, this causes alpha Hydrogen to be pulled away by strong base forming an enolate

2) enolate is strong nucleophile (oxygen has 3 lone pairs) and with electrophile can get a Hydrogen and form an enol

44

Sn2 vs Sn1 Favorability

Sn1: tertiary > secondary > primary

Sn2: Primary > Secondary > tertiary

45

Steric Hinderance

prevention of reactions at a particular location due to a substituent groups.

46

Steric protection

useful in synthesis of desire molecules by making it impossible for nucleophile to reach the most reactive electrophile

can also mask a reactive leaving group by forming a protecting group (aldehyde/ketone to acetal/ketal) to protect the functional groups

47

Steps To Problem Solving

1) Known Nomenclature

2) Identify Functional Groups

4) Identify other reagents

4) Identify the Most Reactive Functional Groups

5) Identify First step of the Reaction

6) Consider Steroselectivity