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ORGANIC - BRUICE 8E

CH. 5 - ALKENES

CONCEPT: INDEX OF HYDROGEN DEFICIENCY (STRUCTURAL)

A saturated molecule is any molecule that has the maximum number of hydrogens possible for its chemical structure. The

rule that we use for this is _____________.

● Any molecule that has less than __________ number of hydrogens is considered to be __________________.

EXAMPLE: How many hydrogens must the following carbon skeletons contain to be saturated? Are they missing any?

IHD rules give us the ability to quickly determine which molecules are more saturated and which molecules are less

saturated with hydrogen.

● 1 IHD = Compound is missing ___ hydrogens.

□ Rings/Double bonds = _____

□ Triple Bonds = ______

EXAMPLE: What is the degree of unsaturation of the following compounds?

ORGANIC - BRUICE 8E

CH. 5 - ALKENES

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CONCEPT: INDEX OF HYDROGEN DEFICIENCY (MOLECULAR FORMULA)

□ Molecular Formula:

- When given only the molecular formula of the molecule use the following rules.

(Theoretical # H’s – Actual # H’s) / 2 = IHD, where: ● H / X = _______ ● O = ______ ● N = ______

EXAMPLE: What is the IHD for each of the following compounds?

a. C4H7Cl

b. C6H7N

c. C7H12O2

ORGANIC - BRUICE 8E

CH. 5 - ALKENES

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CONCEPT: ALKENES and ALKYNES

□ Alkenes/Alkynes are named by adding the suffix modifier (-________/-________) to the end of the root.

● Alkenes/alkynes receive ___________________ in numbering alkanes

● Location is assigned to the first double bonded carbon

EXAMPLE: Name the following compound:

a.

ORGANIC - BRUICE 8E

CH. 5 - ALKENES

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CONCEPT: DOUBLE BOND ISOMERISM

□ Cis and trans are names given to particular arrangements of double bonds or ____________

● These isomers exist because free rotation around π bonds is ______________________

● When two groups are on the “same side of the fence”, we call them ___________

● When two groups are on “different sides of the “fence” we call them ___________

EXAMPLE: How are the different substituents related to each other?

□ E and Z isomers are similar designations given to _______________________________ alkenes

EXAMPLE: Assign cis/trans isomerism to the following alkenes

The E/Z naming system allows us to assign unique names to _______ and __________substituted alkenes.

● Choose the highest priority groups on both corners of the double bond. How are they related to each other?

- If ___________, assign the letter (E)

- If ___________, assign the letter (Z)

EXAMPLE: Assign an (E) - (Z) designation to the following alkenes if applicable.

a. b.

ORGANIC - BRUICE 8E

CH. 5 - ALKENES

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PRACTICE: Determine the IUPAC names of the following molecules

a.

b.

ORGANIC - BRUICE 8E

CH. 5 - ALKENES

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CONCEPT: GIBBS FREE ENERGY

□ Predicts ____________________________ of reactions. Composed of three terms.

● Enthalpy is the sum of bond dissociation energies for the reaction.

_____ = ___________ bonds = Exothermic _____ = ___________ bonds = Endothermic

● Entropy is a measure of disorder in the system.

_____ = More ordered _____ = More disordered

● Temperature amplifies the effect of entropy on the overall favorability.

□ Some reactions require more than one step to go to completion. The ΔG⁰ is the sum of all the steps.

● Transition states ____________ be isolated. They involve bonds being broken and made at the same time.

● Intermediates ____________ be isolated. They rest at a higher energy state than normal.

ORGANIC - BRUICE 8E

CH. 5 - ALKENES

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CONCEPT: FREE ENERGY DIAGRAMS

□ Atoms save energy by forming bonds. Free energy diagrams show overall changes in potential energy during reactions.

□ Free energy diagrams give us information on the spontaneity and rate of reactions

● Thermodynamics describes favorability. Determined by Gibbs Free Energy

● Kinetics describes rate. Determined by the activation energy of the rate determining step.

EXAMPLE: Describe the favorability and rate of the following free energy diagrams.

ORGANIC - BRUICE 8E

CH. 5 - ALKENES

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CONCEPT: ENTHALPY

□ Bond dissociation energies describe the strength of chemical bonds. They can be determined experimentally.

● Enthalpy is the sum of bond dissociation energies for the reaction.

_____ = ___________ bonds = Exothermic _____ = ___________ bonds = Endothermic

EXAMPLE: Predict the sign and magnitude of ΔH⁰ for the following reaction. Give your answer in units of kilojoules per

mole, and identify whether the reaction is expected to be endothermic or exothermic.

PRACTICE: Predict the sign and magnitude of ΔH⁰ for the following reaction. Give your answer in units of kilojoules per

mole, and identify whether the reaction is expected to be endothermic or exothermic.

ORGANIC - BRUICE 8E

CH. 5 - ALKENES

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CONCEPT: ENTROPY

□ Even if a reaction is highly exothermic, the level of order it requires may make it statistically improbable.

● Entropy is the tendency of a system to take its most probable form.

_____ = More ordered _____ = More disordered

□ There are three phenomena that make reactions more probable. □ All are favored by ___ _____

1. Increasing the Number of Molecules

Reactions that create extra molecules are more probable since there are more ways to arrange them.

2. Phase Transition

Transformation of solid to liquid or liquid to gas is more probable since the molecules will have a greater vibrational freedom.

3. Increasing Molecular Freedom of Motion

Converting cyclic molecules to acyclic molecules are more probable since it increases freedom of rotation.

ORGANIC - BRUICE 8E

CH. 5 - ALKENES

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