CHM136H1 Chapter 1: Chapter 1 Notes
CHM136H1(S) – Textbook à Chapter 1 à 1.1 – 1.10, 1.12
• Organic chemistry is important to us because all living organisms are
made up of organic chemicals, and so are all sorts of things around us
• In the beginning, scientists used to believe that the “organic” substances
isolated from plants and animals behaved differently from the
“inorganic” substances isolated in minerals
o So, many chemists at that time believed that this was all due to a
special “vital force” that was present in these “organic”
compounds (since they come from living things)
o Also believed that the “vital force” in organic compounds was
why organic compounds couldn’t be prepared + manipulated in
the lab like inorganic compounds
o Mid-1800s: increasing evidence surfaced against this “vitalistic
theory” à showed that there’s really no difference between
organic and inorganic compounds
• Organic chemistry – study of carbon compounds
• Carbon…
o Can share 4 valence electrons and form 4 strong covalent bonds
o Can bond to each other, forming long chains and rings
• Not all carbon compounds are derived from living organisms à modern
chemists are able to design and synthesize new organic compounds in
the lab
• REFRESHER: Atom made up of a dense, positively-charged nucleus
surrounded by negatively-charged electrons
o Nucleus = protons + neutrons à contains almost all of the mass
of the entire atom because electrons have negligible mass
2
o # of protons in nucleus has to = # of electrons that surround
nucleus in order for atom to have an overall neutral charge
o Atomic # (Z) gives # of protons (or electrons) of atom
o Mass # (A) gives total # of protons and neutrons in nucleus
o All atoms of a given element must have the same atomic #, but
can take on different mass #s because the # of neutrons can vary
• When true, these atoms are called isotopes
o Atomic mass/atomic weight – weighted-average mass in atomic
mass units (amu) of an element’s naturally-occurring isotopes
• Wave equation – describes the behavior of a specific electron in an atom
o Its solution is a wave function/orbital (Ψ)
• Orbital – describes volume of space around nucleus that an electron is
most likely to occupy à for our purposes, it’ll represent the space where
an electron spends 90% - 95% of its time
o 4 different kinds, each with its own shape
ü s (spherical à nucleus at centre)
ü p (dumbbell-shaped) à the 3 different ones (px, py, pz) in a
given shell are mutually-perpendicular à the 2 lobes of
each p orbital separated by region of zero-electron density
(node)
ü d (4 of the 5 are cloverleaf-shaped, 1 like an elongated
dumbbell with doughnut around middle)
ü f
o organic chemistry focuses on s and p more
o organize into electron shells, which are centred around nucleus
and have increasingly larger size and energy à different shells
contain different #s and kinds of orbitals
o each orbital can only hold 2 electrons
3
o 1st shell contains single s orbital à 1s à 2 electrons total; 2nd
shell contains a 2s and three 2p orbitals à 8 electrons total; 3rd
shell has a 3s, three 3p, and five 3d orbitals à 18 electrons total
• Ground-state electron configuration – lowest-energy state of atom that
lists electron-occupying orbitals
o Can be predicted as per 3 rules:
1) Aufbau principle – lowest-energy orbitals fill up first
a. order = 1s à 2s à 2p à 3s à 3p à 4s à 3d
2) Pauli exclusion principle – only 2 electrons of opposite spin
(denoted by up and down arrows) occupy an orbital
3) Hund’s rule – if 2 or more empty orbitals of equal energy are
available, 1 electron occupies each with same spin first until
all orbitals are half-full
• 1858: A. Kekulé and A. Couper independently proposed that carbon is
tetravalent in all organic compounds à forms 4 bonds
o Kekulé also stated that carbon atoms can bond to one another
to form chains
• 1865: Kekulé suggested that carbon chains can form rings
• 1874: J. van’t Hoff and J. Le Bel proposed that carbon’s 4 bonds aren’t
oriented randomly, but have specific spatial directions (hence 3-D)
o van't Hoff also suggested that carbon’s 4 bonded atoms are
arranged in a tetrahedral fashion, with carbon at the centre
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CHM136H1 Full Course Notes
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Document Summary
Chm136h1(s) textbook chapter 1 1. 1 1. 10, 1. 12: organic chemistry is important to us because all living organisms are made up of organic chemicals, and so are all sorts of things around us. In the beginning, scientists used to believe that the organic substances isolated from plants and animals behaved differently from the. P (dumbbell-shaped) the 3 different ones (px, py, pz) in a given shell are mutually-perpendicular the 2 lobes of each p orbital separated by region of zero-electron density (node) D (4 of the 5 are cloverleaf-shaped, 1 like an elongated dumbbell with doughnut around middle) Le bel proposed that carbon"s 4 bonds aren"t oriented randomly, but have specific spatial directions (hence 3-d: van"t hoff also suggested that carbon"s 4 bonded atoms are arranged in a tetrahedral fashion, with carbon at the centre. Valence shell electrons (bonding or non-bonding) shown only and represented as dots: kekul structures/line-bond structures represent covalent bonds as lines.
