Organic Chemistry Chapter 4: Alkanes and Cycloalkanes

How do you name the parent ring of a bicylic compound?

Figure out how many carbons there are, and name it bicylic+(number of carbons prefix)ane.

Where do you start numbering a bicylic compound?

Start numbering at each of the bridgeheads (The carbons connecting 2 parts of a ring to each other)

What is the purpose of the numbers in brackets in the name of a bicyclic compound?

They are the amount of carbons between the bridgehead carbons.

How do you write the bracketed numbers in a bicylic compound's name?

In descending order.

What is the extra rule of numbering branching groups on a bicyclo-compound?

You must start by going around the longest path first.

What determines the stability of an alkane?

Heat of Combustion.

What is heat of combustion?

the heat of reaction for the complete burning of one mole of a substance

What does Delta-H stand for?

Change in enthalpy

What does a negative Delta-H mean?

The reaction is emitting heat

What does it mean when a reaction is emitting heat?

It's EXOthermic

What does a positive Delta-H mean?

The reaction is absorbing heat.

What does it mean when a reaction is absorbing heat?

It's ENDOthermic

Where does the energy come from in a combustion reaction?

From the breaking of the bonds between the carbons in the Alkane.

Would pentane emit more or less heat then butane?

More, because it has more bonds.

Do alkanes with more branches have a higher or lower heat of combustion?

Lower.

What is potential energy?

Heat of combustion

What is angular strain?

Strain as a result of an argument between the angles of a hybridized orbital and the angles of the shape a cyclo-alkane takes on.

Which results in molecules with higher amounts of potential energy: More Branching or more angular strain

More angular strain.

What is unique about cycloalkanes?

They are not static, they wiggle about and move around if they can.

What are the bond angles in a cyclohexane molecule?

120

Why is the shape that cyclo-hexane usually takes on energetically favorable?

It has 0 angular strain due to its 3-D structure, and 0 torsional strain because every carbon is staggered.

What is a chair-flip?

The result of cyclo-hexane changing conformations.

How can you visualize a chair flip?

Orientate the molecule so it looks like a chair. Flip the part that points down up and vice versa.

How does one draw a chair?

Three sets of parallel lines.

How does one draw in the axial substituents of a chair-cyclo-hexane?

Axial substituents that alternate from pointing up to pointing down.