Chem 250 Midterm 1

molecular orbitals

likelihood of finding electrons in space around molecule

resonance structures

used to describe delocalization of pi electrons in molecule

hydrocarbons

unreactive, primarily function as scaffold

saturated

hydrocarbons that contain only single bonds between carbon atoms.

unsaturated

Containing one or more double or triple bonds between carbon atoms

heteroatom

An atom in an organic molecule that is not carbon or hydrogen

intermolecular forces result

charge interactions

electrostatic interactions

that arise from the attraction or repulsion between charged particles or polar molecules, full formal charges, strongest IMF

dipole-dipole

interactions that occur between polar molecules due to the attraction of positive and negative ends

hydrogen bonding

a strong type of dipole-dipole interaction that occurs when hydrogen is bonded to highly electronegative atoms like oxygen, nitrogen, or fluorine.

London dispersion

forces are weak intermolecular forces that arise from temporary shifts in electron density in non-polar molecules

conformations

different spatial arrangements of a molecule that can occur due to rotation around single bonds.

torsional strain is minimum in

staggered conformation

staggered conformation

front and back groups are as far apart as possible, least torsional strain therefore lowest energy

steric strain

repulsive force between the electron clouds of atoms that are close to each other nut not directly bonded

angle strain

bond angles that do not permit maximum orbital overlap between atoms of a molecule

equatorial position

the position in a cyclohexane ring where substituents are located in the plane of the ring—>chair conformer

constitutional isomers

same molecular formula, different connectivity

stereoisomers

same molecular formula, connectivity, different arrangement of atoms in space

enantiomers

stereoisomers that are non-superimposable mirror images (chiral)

chirality

non-superimposable on their mirror image

diastereoisomer

stereoisomers that are non-superimposable, non-mirror images

meso compounds

molecules that contain more than 1 stereocenter and have superimposable mirror images

how does resonance effect organic molecules

greatly stabilized by the delocalization of pi electrons

hybridization

of atomic orbitals to form new hybrid orbitals that can accommodate bonding (sp2, etc)

formal charge

formal charge= group# - #of bonds- #of non-bonded electrons

aldehyde

alkanes

alkenes

alkynes

aromatic rings

alcohols

ethers

aldehydes

ketones

carboxylic acid

esters

acid halides

hydrates

hemiacetals

acetals

amines

nitros

nitriles

imines

halides

thio-

polar

A molecule with a distribution of electric charge, resulting in a positive and negative end. Have electronegativity

non-polar

A molecule that has an even distribution of electric charge, resulting in no distinct positive or negative ends.

axial and equatorial groups

axial: chair six groups pointing directly up/down

equatorial: chair six groups pointing outwards

achiral

A molecule that cannot be superimposed on its mirror image, indicating it has no chiral centers.

stereogenic centre

A carbon atom bonded to four different substituents, leading to non-superimposable mirror images.

R/S descriptors

stereogentic centre, finding way of rotation via priority around centre

R= right/clock wise

S= left/counterclockwise

meso

A compound with multiple stereogenic centers that is superimposable on its mirror image, resulting in no optical activity.

E/Z configurations

E indicates higher priority groups are on opposite sides, while Z indicates they are on the same side.

sigma bond

A type of covalent bond formed by the direct overlap of atomic orbitals, allowing for free rotation around the bond axis.

pi bond

A type of covalent bond formed by the lateral overlap of p-orbitals, allowing for electron sharing between atoms. Pi bonds are typically found in double and triple bonds.

How to use IUPAC naming

1. determine principal characteristic group

2. identify parent chain

3. choose appropriate root word

4. identify double or triple bonds

5. identify side chains or lower functional groups

6. assign E/Z system

how to show overall transformation

number different steps around the same arrow

types of arrows

—> irreversible

<==> reversible

<=—> biased reversible

←→ relates resonance structures

nucleophile

donates an electron pair to form a chemical bond in a reaction, typically seeking positively charged or electron-deficient sites.

electrophile

accepts an electron pair from a nucleophile during a chemical reaction, often possessing a positive charge or a partial positive charge.

what does a reaction coordinate show

relative energies of species in a reaction

define starting materials, intermediates, and products

Starting materials are the reactants at the beginning of a reaction, intermediates are transient species formed during the reaction, and products are the final substances produced at the end.

transition states

what compound(s) look like while undergoing transformation

activation energy

energy difference between starting material/intermediate and transition state for specific reaction

exergonic

lower in energy than the starting materials

endergonic

higher in energy than the starting materials

electron delocalization

large amount of stabilization, more resonance forms the more stable

Factors of importance for resonance

1. full octets

2. fewest formal charges

3. negative formal charges on electronegative

How to identify sigma and pi bonds

1 single=1s

1 double= 1s and 1p

1 triple= 1s and 2p

How to do sp

butane conformational

Superimposable

structures that can be overlaid on each other without any differences in their arrangement.