Chemistry Key terms

Isomer

Different compounds that have the same formula. Two major types: constitutional isomer and stereoisomer

Constitutional Isomers

Differing in connectivity but having the same molecular formula. This means they are NOT identical and the different isomers share different properties (such as mp and bp).

Stereoisomers

Same molecular formula, same connectivity, different spatial arrangements. not superimposable

Conformational Isomers

Not to be confused with constitutional isomers as these do have the same connectivity and same molecular formula. They are a type of stereoisomer that are different from configurational isomers (chemicals where the bonds have to be broken: enantiomers and diastereomers). The bonds only need to be rotated spacially (no bonds need to be broken).

Configurational Isomers

Sub group of stereoisomers where the bonds have to be broken and not rotated. Consists of Enantiomers and Diastereomers.

Epimer

Type of Diastereomer that only differs at one chiral center.

Enantiomer

Type of configurational isomer (stereoisomer) where it is a mirror image but not superimposable

Diastereomer

Type of configurational isomer (stereoisomer) where it is NOT a mirror image and not superimposable

identical

exact same molecular formula, same connectivity, AND superimposable

Geometric stereoisomers

Unlike chiral stereoisomers, the geometry of the ring or alkene locks the arrangements in place. can be described with cis/trans.

if a reaction shows +H, it is (exothermic or endothermic)

endothermic

exergonic reactions favor

products

endergonic reactions favor

reactants

if a reaction shows -H, it is (exothermic or endothermic)

exothermic

if a reaction shows +G, it is (exergonic or endergonic)

endergonic

if a reaction shows -G, it is (exergonic or endergonic)

exergonic

In exergonic reactions, reactants have ___ energy than products

more

In endergonic reactions, reactants have ___ energy than products

less

To determine what makes a good nucleophile, use the ___ rules

CARIO

CARIO

Charge, Atom, Resonance, Induction, Orbital

Types of nucelophiles

neg charge, induction (partially negative charges), lone pairs, pi bond (alkenes)

How does the Atom determine a better/stronger nucleophile

Polarizability- larger and lower on the periodic table = better nucleophile

How does the Resonance determine a better/stronger nucleophile

Less resonance = more unstable = stronger nucleophile

How does the Induction determine a better/stronger nucleophile

needs to have a slighty negative charge

How does the orbital determine a better/stronger nucleophile

sp3 > sp2 > sp

electron-rich species that can donate a pair of electrons

nucleophiles

electron deficient species that can accept a pair of electrons

electrophile

Types of electrophiles

empty orbital/positive charge (usually carbocation), induction (partially positive), ketones (carbonyl attached to two R groups)

The relationship between electronegativity and strength of nucleophile

greater electronegativity = weaker nucleophile

Best atom for nucleophile

Sulfur - larger atom size and polarizability

How does the Charge determine a better/stronger nucleophile

more negative charge = stronger nucleophile

_____ is when electrons in a nearby C–H or C–C single bond "help out" an adjacent atom that is electron-deficient or has an empty orbital. (neighboring bond shares a little bit of its electron density to stabilize a nearby positive charge or radical.)

hyperconjugation

How does hyperconjugation increase in stability

increasing the substitution (primary, secondary, tertiary) as positive charge is distributed more across more carbons or sigma bonds).

It is very hard for what substitution (primary, secondary, tertiary) to undergo hyperconjugation

methyls and primaries (extremely unstable)

__ happens when a hydrogen move from one carbon to the carbon right next to it to make a more stable carbocation. (called 1-2 shift cause hydrogen moves only one carbon over)

1,2-hydride shift

when is the only time a 1,2-hydride shift happens

When it increases the substitution, making the carbocation more stable. It can only be one sigma bond away

An entire CH₃ (methyl) group moves with its bonding electrons to the adjacent carbocation.

1-2 methyl shift

Proton transfer rxns are typically ___

reversible

If a new C-C sigma bond is formed, then its typically ____

irreversible

If a nucelophile attacks a weak leaving group, the reaction is generally ___

irreversible

If a reaction’s pKa difference is __ or more, it is generally irreversible

10 (ten)

carbocation rearrangements are generally ___

irreversible

Le Chatelier’s principle

Concerted

happening all in one instant