Home > Chemistry, Organic chemistry > Chemistry 51A Lecture 12 Notes 10/26/009

Chemistry 51A Lecture 12 Notes 10/26/009


Today is a 37 minute lecture on conformations of cyclohexane.



Cyclohexane has boat and chair conformations.  The chair stands like a three-legged stool.   During ring flips, axial hydrogens turn equatorial.  Equatorials turn axial.

In the half chair conformation, 5 carbon atoms are coplanar.  The half chair is a transition state that is high energy. 

Keep going and you get a rowboat.  There is much eclipsing.  A twist will stabilize the rowboat.  The twist is stable.  The half chair is 10 kcal/mol above the chair conformer, the boat is 7  and the twist is 5.  The half chair has alot of eclipsing interactions. 

Conformation         Energy

Chair                         0 kcal/mol

Half Chair                +10

Boat                            +7

Methylcyclohexane.  This is an equatorial conformer.  The axial confermer stands on two hydrogens and a methyl goup.  There is one gauche butane in the front and one gauche butane in the back. Each steric hinderance of the axial conformation costs 0.9 kcal/mol or 1.8 kcal/mol more than equitorial. 

At 300K, 95% of methylcyclohexane is in the equitorial conformer.  5% is in the gauche conformer. 

Flipping cyclohexane costs 10 kcal/mol.  At room temperature, the border is crossed 10 million times.

Tert-butylcyclohexane.  Ring flip to put the t-butyl into the axial position.  This molecule has really bad 1,3-diaxial interactions. 

Cis – 1-tert-butyl -4-methylcyclohexane.  Trans puts the functional groups on the same side of the ringe.  The t group axial with the methyl group equatorial.  This molecule needs to make a choice.  It often choses the t group equatorial with the methyl group axial. 


Aging: oxygen, UV light, water, heat

Electronegativity: NOF Cl Kr

Alkane CnH2n+2

Alkene CnH2n

Alkyne CnH2n-2

Most important cyclic molecules: Benzene C6H6/Naphthalene C10H8

Moving formations: column line wedge vee eschelon

When not moving: herring bone and coil

Transversing Terrain: traveling, traveling overwatch, bounding overwatch

breaking bonds takes energy, making bonds releases energy

Loads on average were: – fighting load: 63 lbs – approach march load: 101 lbs – emergency approach march load: 132 lbs

One well-established norm is that a soldier cannot sustain a load greater than one-third of his body weight over time.

Noble gases: He, Ne, Ar, Kr, Xe, Rd

Types of bonding: ionic >1.7, polar covalent between, non polar <0.5

PV = nRT

METT TC mission enemy troops terrain time civilians

SALUTE size activity location unit time equipment

2s 6p 10d 14f

KE electron = E photon – Ionization Energy

Tissue: epithelial, connective, nervous, muscular

Epithelial: simple/stratified/pseudostratified cuboidal/columnar/squamous

  • single covalent bond – 1 shared pair
  • double covalent bond – 2 shared pairs
  • triple covalent bond – 3 shared pairs

Bond energy: single < double < triple

Bond length: single < double < triple


Alkanes (50)


Alkene (44)

Alkyne (25

HF +3.2

HCl -7

HBr -9

HI -10 NH3 38 L

RCOOH (4-5)

HF (3.2)

NH4+ (9.26)

H2O (15.7)

ROH (17)

RSH (11)

H30+ (-1.7)

pKa = – log Ka

Spectroscopy: emission/absorption

A = e l c

IGL: point source, random motion, elastic collisions, high temp, low pressure

6 strong acids:

  • HCl
  • H2SO4
  • HNO3
  • HClO4
  • HBr
  • HI

The stronger the acid, the higher the Ka, the weaker the conjugate base.

hydrogen helium

lithium beryllium boron carbon nitrogen oxygen fluorine neon

sodium magnesium aluminum silicon phosphorus sulfur chlorine argon

potassium calcium scandium titanium vanadium chromium manganese iron cobalt nickel copper zinc gallium germanium arsenic selenium bromine krypton

rubidium strontium yttrium zirconium niobium molybdenum technicium ruthenium rhodium palladium silver cadmium indium antimony tin tellurium iodine xenon

cesium barium lutium hafnium tantalum tungsten rhenium osmium iridium platinum gold mercury thallium lead bismuth polonium astatine radon

SWAT – snipers, entry team, inner perimeter/gas people

AOR = area of responsibility

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