orgo 1 - exam 2

constitutional isomers

differ in how atoms are connected

not constitutional isomers

cis and trans disubstituted cyclohexanes

spatial relationships

cis and trans describe

stereoisomers

isomers that posess two or more groups that differ in their spatial relationship

superimposable

identical objects are

enantiomers

mirror images that are non-superimposable

hands

basic example of enantiomers

stereogenic center

the center of an atom form which the stereoisomers originate

tetrahedral carbon with 4 different substituents

the stereogenic center is usually

chiral

any molecule that does not superimpose with its mirror image

achiral

superimposable mirror images

atomic number

we assign priority numbers on stereogenic substituents based on

next atom

when the first atom fails to differentiate substituents, you move to

directly away

physically rotate the stereogenic center to place the least priority group

clockwise or counterclockwise

determine if priority numbers increase

R rectus or right

clockwise

S sinister (left)

counterclockwise

single enantiomer

a single stereogenic center can only give rise to a

enantiomer

switching any two substituents on the stereogenic center gives

properties

in an achiral environment, enantiomers have the same

diastereomers

two molecules differing in some aspect of spatial relationships but are not mirror images

enantiomer/diastereomer

two or more stereogenic centers can lead to

2^n

equation explaining the maximum number of possible stereoisomers

conditions

diastereomers can have different properties under any set of

polarimeter

produces chiral environment, projects plane polarized light onto a sample and measures whether the emergent light has rotated relatively

specific rotation

observed rotation corrected for concentration of the sample and length of the cell in a polarimeter

stereoisomeric products

chemical reactions routinely generate

top and bottom

trigonal planar radical presents the same environment to halogenation from the

enantiomers of equal energy

halogenation of trigonal planar radicals produce

chiral product

chiral reactant halogenation produces

preserves chiral characteristic

preserving the chiral stereocenter

achiral intermediate

destroying chiral stereocenter produces

diastereomers

preserving stereocenter as well as producing another stereocenter produces

different

two pathways leading to producing diastereomeric products are

lewis base

electron pair donor

lewis acid

electron pair acceptor

carbon with electronegative group

lewis acid is commonly

concerted reaction

reaction mechanism involving no intermediates like a radical

bimolecular reaction

requires reactants collide with sufficient energy and correct orientation

nucleophile

lewis basee

electrophile

lewis acid

leaving group

conjugate base, leaves with electron pair

sigma star orbital

what orbital does the nucleophile interact with

most stable leaving group

nucleophile displaces

partial positive

nucleophile interacts with what on carbon

transition state

carbon is sp3 hybridized except in _ where it is sp2 hybridized

Sn2 reaction

bimolecular substitution reaction abbreviation

structure of electrophile and nucleophile

leaving group stability

solvent polarity

factors affecting reaction efficiency

reactivity

substitution at carbon bearing leaving group increases steric repulsion and reduces

neopentyl

relationship between primary carbon with leaving group and adjacent quaternary carbon

sterically destabilized

as sites adjacent to carbon undergoing nucleophilic attack become progressively more substituted and the Sn2 transition state becomes more

uncharged equivalents

charged nucleophiles are stronger than their

hydroxide

OH-

alkoxide

OR-

basicity

nucleophilicity often parallels

sterics

diminishes nucleophilicity similarly to elecrophiles

transition states

in Sn2 reactions what is the most crowded point during the reaction

accelerates reaction

any effect that minimzes the crowding in Sn2 reactions

polarizability

nucleophile electonegativity having a larger hold over electrons, reducing crowding, as well as enhancing the dipole on the electrophile

size

basicity

polaizability

important characteristics of nucleophiles

leaving group

same thing as the conjugate base in bronsted lowry acid base reactions

weak bond

stabilizes the electron pair

good characteristics of a leaving group

inert

solvents must be _ towards the reactants and products in an Sn2 reaction

highly polar

the transition state of an Sn2 reaction is

stabilize

solvents can do this to transition state of an Sn2 reaction and therefore accelerate the reaction

charge

polar solvents help support _ of Sn2 transition state

dimethylsulfoxide

DMSO

n,n-dimethylforamide

DMF

DMSO

DMF

acetonitrile

acetone

methanol

common polar solvents

reactants and products

solvents can also impact stability of

polar protic solvents

stabilize both the cation electrophile and anionic nucleophile

polar aprotic solvents

no hydrogen bonding hydrogen, only able to stabilize the cation electrophile, leaving unstable and reactive nucleophile

accelerate reaction

polar aprotic solvents can

sterics

prevent polar aprotic solvents from effectively solvating the nucleophile

larger nucleophiles

less effectively solvated and therefore remain reactive even in polar solventsi

inversion of configuration

substitution at a 2 prime carbon that is a stereocenter proceeds with

sterics

bonds via substitution on tertiary carbons are unlikely during Sn2 reactions due to

make electrophile very reactive

how to induce substitution reaction on tertiary carbon

Sn1

unimolecular nucleophillic substitution

ionizing alkyl halide

how are Sn1 reactions initated

heterolytic bond dissociation

Sn1 reactions require very polar solvent and high temp to affect

solvent

in Sn1 reactions the nucleophile is usually the

multistep

Sn1 reaction has

reaction rate

depends on largest activation barrier (rate determining step)

carbocation

reactive intermediate in Sn1 reactions

carbocation stability

reaction rate in Sn1 reactions depend on

increases rate

stabilizing the carbocation lowers the largest activation energy needed to break C-X bond in Sn1 reactions and therefore

stability

what trend is opposite between Sn2 and Sn1 reactinos

radicals

carbocations are electron deficient similarly to

hyperconjugation

resonance

electron deficient radicals and carbocations are stabilized by the same interactions such as

anion

in Sn2 reactions the leaving group must depart as an

dielectric constant

measure of solvant polarity

inversion

Sn2 reactions proceed with

racemization

Sn1 reactions proceed with

racemization

converting optically active reactant to racemic (optically inactive) product

racemate

enantiomeric products formed in equal amounts

polar aprotic

most common solvent in sn2 reactions

SN2

solvent does not function as nucleophile in which reaction

polar protic

solvent most common in Sn1 reactions

solvolysis

solvent often functions as nucleophile in Sn1 reactions