Vocab Review - (CH. 4)

Alkanes

Simple hydrocarbons (C and H), all σ bonds; (NO π bonds!)

⭐NOTE:

• Cycloalkanes form a ring

• All of their names end in “-ane”

Cis/trans

Cis = on the SAME side of the ring

Trans = on OPPOSITE sides of the ring

**add this prefix to the beginning of the name

Constitutional Isomers VS. Identical Compounds

• Constitutional isomers = the same molecular formula but different connectivity

• identical compounds = the same compound represented in different ways (can be rotated in space)

Heat of Combustion (Stability)

How stable is the molecule as a whole?

• more heat released = LESS stable molecule

• lower energy molecules = MORE stable

Barrier of Rotation

Energy needed to rotate around a single bond (torsional strain)

Angle Strain

Energy associated with forcing bonds into non-VSEPR bond angles

Newman Projections

• Dot = Front

• Circle = Back

• wedge = out towards you

• dash = away from you

Conformations:

Staggered VS. Eclipsed

Staggered = same distance (and can see all bonds behind)

Eclipsed = bonds infront BLOCK molecules behind (cannot see)

Steric Interactions:

Anti VS. Gauche

Anti = Methyl groups are FARTHEST apart (180 angle usually)

Gauche = Methyl groups (or any 2 of the same molecule enxt to eachother) experience a gauche interaction

Steric Hinderance

stuff bumps into each other (big bulky things bump into each other)—> ⭐big bulky things WANT to be spread out⭐

you do NOT want steric hinderance!!!!!

When you chair flip….

all axials BECOME…

all equatorial BECOME….

equatorial

axial

Axial bonds cause….

axial strain (creating higher energy)

for wanting lower energy….MORE equatorial is good