OCHEM 1 FInal

Constitutional isomers

Constitutional isomers

share the same molecular formula but have different connectivity of atoms and different physical properties

Covalent Bond

results when two atoms shares a pair of electrons

are illustrated using lewis strictures which electrons are represented by dots

Induction

these are exhibited by polar covalent bonds causing a partial negative or partial positive charge , these can be shown in electrostatic potential maps

Valence Bond theory

treats every bond as the sharing of electron density between two atoms as a result of constructive interference of their atomic orbitals

Molecular Orbital theory

uses Math method to form molecular orbitals each one is associated with the entire molecule rather than just two atoms

Bonding MO - constructive interference between its two atomic orbitals

Antibonding MO- results from destructive interference

Atomic Orbital

is a region of space associated with an individual atom, while a molecular orbital is associated with an entire molecule

Bond line Structures contain dashes and wedges what do these groups represent

wedges - represents a group coming out of the page

dashes- represent a group behind the page

what does resonance stability refer to

it refers to the delocalization of electrons via resonance

Resonance structures are most easily drawn by looking for the following patterns

1. an allylic lone pair

2. an allylic carbocation

3. a lone pair adjacent to C+

4. a pi bond between two atoms of differing electronegativity

5. Conjugated pi bonds enclosed in a ring

Rules to Identify the significance of resonance structures

1. the most significant resonance forms have the greatest number of filled octets

2. the structure with fewer formal charges is more significant

3. a structure with a negative charge on the more electronegative element Will be more significant ,similarly , a positive charge will be more stable on the less electronegative element

4. resonance forms that have equally good lewis structures are described as equivalent and contribute equally to the resonance hybrid

Bronsted- Lowry Acid

is a proton donor

Bronsted-Lowry Base

is a proton acceptor

a strong acid has a LOW

PKA

a weak acid has a HIGH

PKA , this is favored by equilibrium

factors to consider when comparing the stability of anionic conjugate bases

1. which atom bears the charge

2. resonance which will stablize a negative charge

3. induction - electron withdrawing groups such as halogens stablize a nearby charge via induction

4. orbitals - a negative charge in an sp-hybridized orbital will be closer to the nucleus and more stable than a negative charge in an sp3 hybridized orbital

Cations

positively charged species

Lewis Acid

is an electron pair acceptor

Lewis Base

is an electron pair donor

Alkanes / Saturated hydrocarbons

hydrocarbons that lack pi bonds

Naming Rules

1. identify parents chain

2. name the subtituents

3. number the carbons of the parent and assign a locant number to each substituent

4. assemble the substituents alphabetically placing locants in front of each substituent for identical ones your di,tri,tetra,penta,hexa

bicycloalkanes

is an alkane that has two rings that are connected to one another

to number the parent , travel first along the longest path connecting the bridgeheads

equilibrium will favor the chair conformation with substituent in the _____ position

Equatorial position ,

Stereoisomers

have the same connectivity of atoms but different in their spatial arrangement

Chiral

not superimposable and have 4 different groups attached to their centers

Enantiomer

a compound with one chiral center will have one non superimposable mirror image, mirror images

racemic mixture

a solution containing equal amounts of both enantiomers

formula for finding the number of stereoisomers

2^n , n= the number of chiral centers

meso compound

contains multiple chiral centers but is achiral because it possesses reflectional symmetry

Fisher projections

are drawings that convey the configuration of chiral centers without the use of wedges and dashes

heat of reaction

is a measure of the energy exchanged between the system and its surroundings

bond dissociation energy

the amount of energy necessary to accomplish hemolytic bond cleavage

producing radicals

Exothermic reactions

involve a transfer od energy from the system to the surroundings

Endothermic Reactions

involve the transfer of energy from the surrounding into the system

Entropy

the disorder of a system

A low energy of activation corresponds with

a fast rate

Catalyst

speed up the rate of reaction by providing an alternate pathway with lower Ea

On an energy diagram what does each Peak and valley stand for

Peak- transition state

Valley - intermediate

Nucleophile

is an electron rich molecule or ion that is capable of donating a pair of electrons known as Lewis Bases

Electrophile

is an electron-deficient molecule or ion that is capable of accepting a pair of electrons known as Lewis Acid

Carbocation

are ions In which a carbon atom bears a positive charge as a result of a an empty p orbital and are electrophlilic

Types of arrow pushing patterns

1. Nucleophilic attack

2. loss of a leaving group

3. proton transfer

4. rearrangement

what is the most common type of rearrangement

is a carbocation rearrangement in which a carbocation undergoes a hydride or methyl shift to produce a more stable carbocation tertiary carbocations are the most stable

what are good leaving groups

conjugated bases of strong acids

Alpha positon

is the carbon atom connected directly to the halogen

beta position

carbon atoms connected to the alpha position

SN2 reactions

1. proceed via inversion of configuration because a nucleophile can inly attack from the back side

2. they cannot be performed with tertiary alkyl halides

3. will generally not occur if there are 3 subsitutents at a beta position

E2 reactions

creation of alkenes

trans over cis is favored in the alkene

Zaitsev product

favors the more substituted alkene

Hoffman Product

favors the less substituted alkene

Sn1

1. loss of leaving group

2. nucleophilic attack

favored by polar protic solvents

tertiary alkyl halides and allylic and benezylic halides

Protic Solvents

contain a hydrogen atom connected directly to an electronegative atom

favored by Sn1 reactions

polar aprotic solvents

lack a hydrogen connect directly to an electronegative atom

addition reactions

the addition of two groups across a double bond

Hydrohalogenation

the addition of H and X across a pi bond where X is a halogen

Markovnikov additon

something will be placed at the more substituted position

anti-Markovnikov additon

something will be placed in the less substituted position

in the presence of peroxides, addition of HBr

Hydration

addition of water (H and OH ) across a double bond

acid catalyzed hydration

addition of water in the presence of an acid which generally proceeds via Markovnikov addition

proceeds via a carbonation intermediate which is attacked by water to produce an oxoniuim ion followed by deprotonation

Oxymercuration- demercuration

achieves hydration of an alkene without carbocation rearrangements

the reaction is believed to proceed via a bridged intermediate called a mercurinium ion

Hydroboration Oxidation

can be used to achieve anti-mark addition of water across an alkene happens via syn addition

a borane is attacked by a pi bond triggering a simultaneous hydride shift

Catalytic Hydrogenation

the addition of H2 across an alkene in the presence of a metal catalyst via syn addition

Halogenation

involves the addition of X2 either Br2 or Cl2 across an alkene

Bromination

proceeds via a bridged intermediate called a bromonium ion done via anti addition sn2 process

in the presence of water the product is bromohydrin or a chlorohydrin and the reaction is called halohydrin formation

Dihydroxylation

reactions are characterized by the addition of OH and OH across an alkene

a two step procedure for an anti- involves the conversion of an alkene to an epoxide followed by acid catalyzed ring opening

Ozonolysis

can be used to cleave a double bond and produce two carbonyl groups

what Is a triple bond composed of

three seperate binds

one sigma bond

and 2 pi bonds

Alkynes naming

the parent chain must include the triple bond within it

the triple bond should receive the lowest number possible

dissolving metal reduction

will convert an internal alkyne into a trans alkene

this reaction involves an intermediate radical anion and fishhook arrows

Acid-Catalyzed Hydration of alkynes

is catalyzed by mercuric sulfate (HgSO4) to produce an enroll that can’t be isolated because it is rapidly converted into a Ketone

Tautomers

consitutional isomers that rapidly interconvert via the migration of a proton

an interconversion between and ketone and enol is catalyzed by trace amounts of acid or base

Hydroboration- oxidation

of a terminal alkyne proceeds via an anti mark addition to produce an enol that can be converted in to a aldehyde via tautomerization which proceeds via a resonance stabilized anion called an enolate ion

internal alkynes form what when they undergo oxidative cleavage

2 carboxylic acids

Terminal Alkynes form what when they undergo oxidative cleavage

a Carboxylic acid and Carbon dioxide

Which Radicals are resonance stabilized

Allylic and benzylic radicals

Radical Mechanism

1. Homolytic Cleavage

2. Addition to a pi bond

3. hydrogen abstraction

4. Halogen Abstraction

5. Elimination

6. Coupling

Radical Initiator

is compound with a weak bond that readily undergoes homolytic bond cleavage

Alkyl peroxides and acyl peroxides

Radical inhibitor

is a compound that prevents a chain process from either getting started or continuing

Allylic Bromination

bromination occurs at the allylic position

how can the position of a halogen be moved

by performing an elimination followed by addition

how can the position of a Pi bond be move

by performing an addition followed by an elimination

how can a alkane be functionalized

via a radical bromination followed by elimination to give an alkene

if a carbon skeleton increases

bond forming Is required

If a carbon skeleton decreases

bond breaking , bond cleavage is required

Constructive interference of Waves results in

a covalent bond

a wave with larger amplitude

Destructive interference of waves results in

formation of a node

cancellation of both waves

Straight line alkanes have a higher boiling point than

branched alkanes

Electronegativity increases

to the right of the periodic table and up the periodic table

the more hydrogens attached the higher the

Boiling point

when an acid loses a proton , it always becomes a

conjugate base

Delocalized lone pair

electrons can move and participate In resonance

Atropisomers

a pair of chiral compounds that lack a chiral center

which of the following compound is least acidic

which of the following solvents would be the best for an Sn2 Reaction

acetonitrile

which of the following would be classified as a bulky base

Diisopropylamine

t-Buok

Tea

An __ Solvent such as __, would be most useful in an Sn2 Reaction

Aprotic and acetone

In an E2 reaction, the use of a small base result in the ___. product , characterized as the

Zaitzev

Most substituted

Stereochemistry in an Sn2 Reaction always results in

inversion of stereochemistry at the alpha carbon

most stable radical

allylic

if doubling the concentration of one reactant doubles the rate of reaction, but doubling the other reactant provides no impact on the reaction , which order of kinetics is it

first order

Transition States

a high energy representation of a molecule that is not isolable