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ORGANIC - MCMURRY 9E

CH.7 - ALKENES: STRUCTURE AND REACTIVITY

CONCEPT: STABILITY OF ALKENES

□ Alkenes are also stabilized through _________________________________

● Since this is only possible with -R groups, the more substituted the alkene, the more ________________

EXAMPLE: Rank the following alkenes in order of lowest to highest heat of combustion.



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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?



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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



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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.



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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.



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PRACTICE: Determine the IUPAC names of the following molecules

a.

b.



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CONCEPT: CARBOCATION INTERMEDIATES — STABILITY

□ Carbocations are stabilized by a phenomenon called _________________________________

● Hyperconjugation is the delocalization of charge by the interaction of an empty p-orbital with an adjacent, eclipsed σ-bond

● Since this is only possible with -R groups, the more substituted the carbocation, the more ________________

EXAMPLE: Which of the following alkyl halides would generate the most stable carbocation?



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CONCEPT: CARBOCATION INTERMEDIATES — REARRANGEMENTS

□ Carbocations will rearrange to an adjacent, more stable position if possible. This is called a ___________

● 1,2-Hydride Shift occurs when there is a ____________ located on an adjacent, more stable carbon.

● 1,2-Alkyl Shift occurs when only small __________ groups are located on an adjacent, more stable carbon.

● Ring Expansion occurs when a carbocation is adjacent to a 3, 4 or 5- membered ring.



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PRACTICE: Which of the following carbocations would be likely to rearrange? Draw each rearranged structure below.



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CONCEPT: THE HAMMOND-POSTULATE

□ The Hammond-Postulate more accurately describes what transition states look like. Paraphrased version:

● Transition state that resembles reagents = ____________ ● Transition state that resembles products = ___________

EXAMPLE: Determine which species has higher energy in the following reactions. Identify the transition state as early or

late, and correctly draw it.



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CONCEPT: GENERAL MECHANISM

□ Addition reactions are ones in which 1 ______ bond is broken and 2 new ______ bonds are formed.

● They are the inverse of ___________________ reactions

EXAMPLE: Provide the mechanism for the following addition reaction.



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CONCEPT: MARKOVNIKOV’S RULE

□ When we try to perform addition on asymmetric double bonds, we now get two possible products.

● Markovnikov’s Rule predicts that the carbocation will ALWAYS form on the _________ _______________ carbon




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CONCEPT: HYDROHALOGENATION

General Reaction:




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ORGANIC - MCMURRY 9E CH.7 - ALKENES: STRUCTURE AND …lightcat-files.s3.amazonaws.com/packets/admin_organic-2-organic-chemistry-mcmurry-118...ORGANIC - MCMURRY 9E CH.7 - ALKENES: STRUCTURE