CHEM301: Chapter 1 - Structure & Bonding

resonance structure

One of multiple valid Lewis structures differing only in electron placement.

resonance hybrid

The actual structure of a molecule, representing an average of all resonance forms.

constitutional isomers

Compounds with the same molecular formula but different connectivity.

stereoisomers

Compounds with the same connectivity but different spatial arrangement.

enantiomers

Non-superimposable mirror-image stereoisomers.

heteroatom

Any atom in an organic molecule that is not carbon or hydrogen.

hybridization

Mixing of atomic orbitals to form new orbitals for bonding (sp, sp², sp³).

What does “degree of unsaturation” tell you?

The number of rings and/or double bonds in a molecule.

What does a fractional degree of unsaturation mean?

The molecule cannot exist as a neutral, closed-shell structure.

What is VSEPR theory?

Electron groups repel each other and spread out to minimize repulsion.

Hybridization for 4 electron groups?

sp³ (tetrahedral).

Hybridization for 3 electron groups?

sp² (trigonal planar).

Hybridization for 2 electron groups?

sp (linear).

What is a functional group?

A specific group of atoms that determines reactivity.

Jöns Jakob Berzelius

A Swedish chemist who introduced modern chemical notation using element symbols and subscripts (such as H₂O), helping standardize how chemical formulas are written.

Friedrich Wöhler

A German chemist who showed that organic compounds could be made from inorganic substances by synthesizing urea, disproving the idea of vitalism.

what are organic compounds mainly made of?

carbon and hydrogen, and they often also contain oxygen, nitrogen, sulfur, phosphorus, and halogens.

formula charge

Formal Charge = valence electrons − (nonbonding electrons + number of bonds)

what does the “R group” mean in organic chemistry?

A placeholder for the “rest of the molecule,” usually a carbon chain or carbon-based substituent, whose exact identity doesn’t matter for the reaction or concept being discussed.

solid line

A bond that lies in the plane of the paper.

Solid wedge

A bond that comes out of the plane toward you.

Dashed wedge

A bond that goes behind the plane, away from you.

Diastereomers

Stereoisomers that are not mirror images of each other and have different physical and chemical properties.

how do enantiomers and diastereomers differ?

Enantiomers are non-superimposable mirror images of each other and have the same physical properties (except how they rotate plane-polarized light).

Diastereomers are not mirror images and have different physical and chemical properties.