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Chemistry 51A: Lecture 1 Notes


This is our new “official”  lecture series.  These lectures are the usual 50 minutes long, indicating that this is a Monday/Wednesday/Friday 3 credit class.  This series covers organic chemistry.

This will be a difficult course without many hours of practice.  Ochem is very different from most chemistry, like another language.  It is the number one eliminator of doctors.  Therefore, learn what you are able in the time you can.  This is a treat – you get realistic noises like coughing, zipping, people walking in late.


Here is a webcast site:


And finally, a place to test oneself:



Electronegativity – the ability to hog and rip off electrons.  Organic chemists have a very narrow view of the periodic table.

H 2, Li 1, Na .9, C 2.5, N 3, O 3.5, F 4

Electronegativity differences lead to bond polarization and the setting up of dipoles within a molecule.  When the difference is greater than two, it is an ionic bond.

Formaldehyde is COH2.  It has a dipole moment and a polar covalent bond.

The lewis structure is all about octet satisfaction.  The number of electrons are valence electrons.  Carbon has 4, nitrogen 5, oxygen 6, fluorine 7, hydrogen 2.

DMSO is dimethyl sulfoxide or (CH3)2SO.  It’s used in the lab and in sports medicine.  Get used to drawing methyl blocks.

Formal charge is a book keeping trick to monitor charge.  NH4+ is ammonium ion.

Number of valence electrons in – number of bonding electrons given= FC

For NH4+, H is 1 – 1 = o and N = 5 – 4 = +1.

Explode all of the bonds into dots – each bond has two electrons.  H. .C. .S

DMSO: H = 1-1 = 0, C = 4 -4 = 0, S = 6 -5 = +1, O = 6 – 7 = -1.

CH3N3 is methyl azide which has several resonance structures.

The bread and butter of most organic chemists is the lewis dot structure.

CH3CO2- is the acetate anion.  The negative charge is on one of the oxygens.

The most famous resonant molecule is benzene, C6H6.  Resonance is when a strucutre has more than one correct lewis dot structure.  Both structures exist at the same time.


PV = nRT

Electronegativity – NOF Cl Kr

pKa = -log Ka

FC = V - N - {B over 2}

The strongest acid in water is H3o+, the strongest base is OH-

nucleophiles attack electrophiles

Nucleophiles like positive charge, electrophiles like negative charge

P = mv

c = wf

G = -RT ln K


  1. Charge
  2. Electronegativity
  3. Solvent
  4. Steric hindrance

G = H – TS

Nucleophile = Nu = A species that donates a pair of electrons to form a new covalent bond

Lewis bases donate electrons, lewis acids accept electrons

  1. September 18, 2012 at 3:03 pm

    Great links! I’m really looking forward to this class. Time to dust off the chem1A notes.

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