Organic Chemistry Midterm 1 Review

Flashcards for CHEM 2020 - ORGANIC CHEMISTRY MIDTERM 1 NOTES

Organic Chemistry

Study of carbon compounds.

Atomic Orbital

Describes the probability of finding an electron around an atom.

Shape of 's' orbitals

Spherical.

Shape of 'p' orbitals

Dumbbell shape with a node in the middle.

Valence Electrons

Outermost shell (valence orbitals).

Octet Rule

Elements are most stable when they have 8 electrons in their valence shell.

Ionic bond

Electrostatic attraction between species of opposite charges.

Covalent bond

Sharing of electrons between atoms.

Lewis Structures

2 electrons for each bond and lone pair, all lone pairs and atoms in the molecule are drawn out.

Formal Charges

Method for keeping track of electrons.

Covalent bonds

Result of overlap between atomic orbitals.

Sigma (σ) bond

Direct (head-on) overlap.

Pi (π) bond

Indirect (side-by-side) overlap.

Electronegativity

Ability of an atom to pull electrons toward itself.

Bond Dipole

Difference in electronegativity between two covalently bonded atoms leads to unequal sharing of electrons.

VSEPR Theory

Predicts shapes of organic molecules.

Valence Bond Theory

Considers bonds as localized between a pair of atoms.

Hybrid Orbitals

Mixing the 2s and 2p orbitals of the atom.

sp3 hybrid orbitals

Tetrahedral geometries require…

sp2 hybrid orbitals

Trigonal planar geometries require…

sp hybrid orbitals

Linear geometries require…

Molecular Orbital Theory

Considers electrons as delocalized throughout the entire molecule.

Condensed Structures

Bonds are not explicitly shown, atoms presented as a list.

Line Structure

All bonds between atoms (other than hydrogen) are drawn as solid lines in a zig-zag pattern.

Hydrocarbons

Part of molecules consisting of only C & H.

Saturated hydrocarbons

Contain only single bonds.

Unsaturated hydrocarbons

Contain double and/or triple bonds.

Functional Group

An atom or group of atoms that exhibits its own distinct pattern of chemical reactivity.

Intramolecular Forces

Interaction between atoms.

Intermolecular Forces

Interaction between molecules.

Electrostatic Interactions

Results from the presence of full formal charges.

Dipole-Dipole Interactions

Weak interactions arising from permanent or induced dipoles.

Hydrogen Bonding

Occurs between a hydrogen atom bonded to a very electronegative atom (O or N or F).

London Forces

Attractive interactions that exist between all molecules.

Solvent

Medium in which compounds may be dissolved.

Solute

Material that is dissolved.

Hydrophobic Compounds

Establish only weak London forces, generally insoluble in water.

Hydrophilic Compounds

Polar enough to form favorable intermolecular interactions, generally water-soluble.

IUPAC Name

broken down into prefixes, root names and suffix.

Alkanes

Describes the longest (parent) chain in the molecule and has the suffix “ane”.

Branched Alkanes

Hydrocarbon substituents bonded to the main chain.

Conformations

Different rotational arrangements.

Newman Projections

Best way to judge the relative stability of the conformations.

Torsion Angle

Angle defined by 4 consecutive covalently bonded atoms.

Torsional Strain

Arises from repulsions between electrons in bonds on adjacent atoms.

Steric Strain

E-e repulsion experienced between 2 bulky groups/atoms when forced close.

Angle Strain

Deviation of bond angle from ideal values in a ring.

Torsional Strain (Cyclic)

Eclipsing of bonds on neighboring atoms.

Chair Conformation

Non-planar conformation of cyclohexane free of torsional and angle strain.

Axial Hydrogens

Hydrogens are parallel to the axis of the ring.

Equatorial Hydrogens

Hydrogens are directed outward toward the equator of the molecule.

Monosubstituted Cyclohexanes

When the substituent is in the axial position due to steric strain.

Isomers

Different molecules formed from the same set of atoms.

Constitutional Isomers

Molecules have the same chemical formula, but atoms are connected differently.

Stereoisomers

Have the same bond connectivity, but differ in how atoms are oriented in space.

Configuration

Precise fixed 3D arrangement of atoms and the bonds that connect them.

Enantiomers

Molecules that are non-superposable mirror images.

Chirality

Ability of objects to exist as non-superposable mirror images of each other.

Stereogenic Centers

Atoms that are connected to 4 different groups (sp3 hybridized).

Cahn-Ingold-Prelog (CIP) Convention

Arbitrary but systematic rules for naming chiral centers.

Diastereomers

Stereoisomers that are not enantiomers.

Meso Compounds

Achiral molecules with chiral centres.

Dextrorotatory

Chiral molecule that rotates polarized light clockwise.

Levorotatory

Chiral molecule that rotates polarized light counterclockwise.

Fischer Projections

alternative (old-fashioned) way to represent chiral compounds