ch. 5 - alcohols and alkyl halides: introduction to...
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ORGANIC - CAREY 10E
CH. 5 - ALCOHOLS AND ALKYL HALIDES: INTRODUCTION TO REACTION MECHANISMS (PART.1)
CONCEPT: FUNCTIONAL GROUPS
● We can group several millions of different molecules into subsets of similar _________________________
1. Hydrocarbons
● All carbon groups regardless of size can be symbolized using an _______ group.
● When an alkane is attached to a greater carbon chain, it is given an ________ suffix. (i.e. __________ group)
● Carbons are given a “degree” based on how many other ____________ they are attached to
□ Hydrogens possess the __________ degree as the carbon they are attached to
□ Degrees are expressed as primary, secondary, tertiary and quaternary (1⁰, 2⁰, 3⁰, 4⁰)
EXAMPLE: Determine the degree of the indicated carbons and hydrogens
ORGANIC - CAREY 10E
CH. 5 - ALCOHOLS AND ALKYL HALIDES: INTRODUCTION TO REACTION MECHANISMS (PART.1)
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2. Alkyl Halide _________
● Any –R group directly attached to a halogen.
● The degree of alkyl halide is determined the same way as __________________
The carbonyl ____________ is NOT a functional group, but it is a major component of many functional groups
3. Alcohol ____________ 6. Carboxylic Acid ______________(_________) ● Degree of alcohol is determined the same ● The acid of organic chemistry way as ____
4. Amine ______________ 7. Amide _______________(___________)
Degree of alcohol is determined the same ● Degree of alcohol is determined the same way as ____. way as ____.
5. Ether __________________ 8. Ester __________________(___________)
ORGANIC - CAREY 10E
CH. 5 - ALCOHOLS AND ALKYL HALIDES: INTRODUCTION TO REACTION MECHANISMS (PART.1)
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9. Carbonyls
The term “ carbonyl” is not the proper name of the functional groups because the functionality of the group depends on its location on the carbon chain.
.
● Ketone ______________(__________) ● Aldehyde ______________(__________)
- _______________carbonyl group - _______________carbonyl group
10. Nitrile ________________
11. Benzene
● Directly attached to –R group _______________ (_________)(_____)
● Extra CH2 between –R group _______________ (_____________)(_____)
EXAMPLE: Identify all the functional groups in the following compound. Show degrees where applicable.
ORGANIC - CAREY 10E
CH. 5 - ALCOHOLS AND ALKYL HALIDES: INTRODUCTION TO REACTION MECHANISMS (PART.1)
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12. Other Carbonyl Compounds
● Acyl Chloride (__________) ● Anhydride (_______________)
13. Sulfur Compounds
ORGANIC - CAREY 10E
CH. 5 - ALCOHOLS AND ALKYL HALIDES: INTRODUCTION TO REACTION MECHANISMS (PART.1)
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PRACTICE: Identify all the functional groups in the following compound. Show degrees where applicable.
a.
b.
c.
ORGANIC - CAREY 10E
CH. 5 - ALCOHOLS AND ALKYL HALIDES: INTRODUCTION TO REACTION MECHANISMS (PART.1)
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CONCEPT: ALKYL HALIDES
Alkyl halides are named by naming them as a substituent before the root chain and indicating their location.
● Prefixes: -F ______________, -Cl _______________ -Br ________________ -I ______________
Alkyl halides have NO ________________ when it comes to numbering the direction of the chain.
EXAMPLE: Name the following compounds:
a.
b.
ORGANIC - CAREY 10E
CH. 5 - ALCOHOLS AND ALKYL HALIDES: INTRODUCTION TO REACTION MECHANISMS (PART.1)
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CONCEPT: ALCOHOL NOMENCLATURE
□ Alcohols are named by adding the modifier (-_______) the end of the root.
● Alcohols receive _______________ priority in numbering alkanes
● Locations can be donated _______________ the root “old school” or _______________ the root “new school”
EXAMPLE: Name the following compound:
a.
ORGANIC - CAREY 10E
CH. 5 - ALCOHOLS AND ALKYL HALIDES: INTRODUCTION TO REACTION MECHANISMS (PART.1)
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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.
ORGANIC - CAREY 10E
CH. 5 - ALCOHOLS AND ALKYL HALIDES: INTRODUCTION TO REACTION MECHANISMS (PART.1)
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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?
ORGANIC - CAREY 10E
CH. 5 - ALCOHOLS AND ALKYL HALIDES: INTRODUCTION TO REACTION MECHANISMS (PART.1)
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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.
ORGANIC - CAREY 10E
CH. 5 - ALCOHOLS AND ALKYL HALIDES: INTRODUCTION TO REACTION MECHANISMS (PART.1)
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PRACTICE: Which of the following carbocations would be likely to rearrange? Draw each rearranged structure below.
ORGANIC - CAREY 10E
CH. 5 - ALCOHOLS AND ALKYL HALIDES: INTRODUCTION TO REACTION MECHANISMS (PART.1)
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CONCEPT: INTRODUCTION TO SUBSTITUTION
Previously, we discussed the various ways that acids could react with bases:
□ Recall that in these mechanisms, electrons always travel from ________ density to _______ density
Bronsted-Lowry Reactions: When a nucleophile and electrophile react to exchange a ______________
Lewis Acid/Base Reactions: When a nucleophile and electrophile with an empty orbital react to form a covalent bond
Substitution Reactions take place when a nucleophile reacts with an electrophile that does not have an empty orbital.
□ This generates the need to analyze a new type of conjugate base: the leaving group.
EXAMPLE: Predict the product. Identify all of the chemical species in the following reaction.
● In typical acid and base reactions, we used stability of the conjugate base to determine chemical equilibrium
● In substitution, we use the stability of the leaving group to help determine reaction rate.
ORGANIC - CAREY 10E
CH. 5 - ALCOHOLS AND ALKYL HALIDES: INTRODUCTION TO REACTION MECHANISMS (PART.1)
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CONCEPT: LEAVING GROUPS
Leaving groups break a bond with the electrophile to make it reactive. They are molecules that will remain stable after
accepting an extra electron pair.
□ We use factors affecting acidity to determine which atoms will be most stable after gaining extra electrons.
● Recall that the element effect consists of two trends:
EXAMPLE: Predict which of the following pairs of electrophiles possesses the best leaving group
a. b.
c. d.
□ Due to their high electronegativity, __________ ______________ will be the primary leaving groups for this chapter.
ORGANIC - CAREY 10E
CH. 5 - ALCOHOLS AND ALKYL HALIDES: INTRODUCTION TO REACTION MECHANISMS (PART.1)
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CONCEPT: THE SN2 MECHANISM
□ A negatively charged nucleophile reacts with an accessible leaving group to produce substitution in one-step.
SN2 Properties (Circle One)
● Nucleophile = Strong / Weak
● Leaving Group = Unsubstituted / Highly Substituted
● Reaction coordinate = Transition State / Intermediate
● Reaction = Concerted / Two-Step
● Rate = Unimolecular / Bimolecular
● Rate = k[RX] / k[Nu][RX]
● Stereochemistry = Inversion / Retention / Racemic
● Nickname = ______________________________________
EXAMPLE: Rank the following alkyl halides in order of reactivity toward an SN2 reaction.
ORGANIC - CAREY 10E
CH. 5 - ALCOHOLS AND ALKYL HALIDES: INTRODUCTION TO REACTION MECHANISMS (PART.1)
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PRACTICE: Provide the mechanism and final products for the following reactions.
a.
b.
ORGANIC - CAREY 10E
CH. 5 - ALCOHOLS AND ALKYL HALIDES: INTRODUCTION TO REACTION MECHANISMS (PART.1)
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CONCEPT: THE SN1 MECHANISM
□ A neutral nucleophile reacts with an inaccessible leaving group to produce substitution in two-steps.
The more -R groups, the more substituted the carbocation, the more ________________
SN1 Properties (Circle One)
● Nucleophile = Strong / Weak
● Leaving Group = Unsubstituted / Highly Substituted
● Reaction coordinate = Transition State / Intermediate
● Reaction = Concerted / Two-Step
● Rate = Unimolecular / Bimolecular
● Rate = k[RX] / k[Nu][RX]
● Stereochemistry = Inversion / Retention / Racemic
● Nickname = ______________________________________
ORGANIC - CAREY 10E
CH. 5 - ALCOHOLS AND ALKYL HALIDES: INTRODUCTION TO REACTION MECHANISMS (PART.1)
Page 17
PRACTICE: Provide the mechanism and final products for the following reactions.
□ NOTE: Substitution reactions with neutral nucleophiles require an additional deprotonation step.
a.
b.
ORGANIC - CAREY 10E
CH. 5 - ALCOHOLS AND ALKYL HALIDES: INTRODUCTION TO REACTION MECHANISMS (PART.1)
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CONCEPT: SUBSTITUTION COMPARISON
When given a substitution reaction, use the following two factors to determine the mechanism:
1. Nucleophile Strength SN1 = ___________ SN2 = ___________
2. Leaving Group Substitution SN1 = ___________ SN2 = ___________
EXAMPLE: Provide the mechanism and final products for the following reactions.
a.
b.
ORGANIC - CAREY 10E
CH. 5 - ALCOHOLS AND ALKYL HALIDES: INTRODUCTION TO REACTION MECHANISMS (PART.1)
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CONCEPT: CONVERSION OF ALCOHOLS TO GOOD LEAVING GROUPS
□ Alcohols are terrible leaving groups. If we want to react with them, they need to be transformed.
●They can be converted into ____________ _________________ or ______________ _______________
2o and 3o Alcohols with HX: SN1 mechanism
1o alcohols with HX: SN2 mechanism
ORGANIC - CAREY 10E
CH. 5 - ALCOHOLS AND ALKYL HALIDES: INTRODUCTION TO REACTION MECHANISMS (PART.1)
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CONCEPT: CONVERSION OF ALCOHOLS TO GOOD LEAVING GROUPS
□ SOCl2 and PBr3 are two of the most commonly used reagents to transform alcohols into alkyl halides
●They always proceed with __________________________ of configuration.
1o and 2o Alcohols to RX: SN2 mechanism
EXAMPLE: Determine the mechanism for the following reaction. Draw the final product.
ORGANIC - CAREY 10E
CH. 5 - ALCOHOLS AND ALKYL HALIDES: INTRODUCTION TO REACTION MECHANISMS (PART.1)
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CONCEPT: CONVERSION OF ALCOHOLS TO GOOD LEAVING GROUPS
□ Alcohols can attack sulfonyl chlorides to create sulfonate esters.
●They always proceed with __________________________ of configuration.
Alcohols to Sulfonate Esters:
ORGANIC - CAREY 10E
CH. 5 - ALCOHOLS AND ALKYL HALIDES: INTRODUCTION TO REACTION MECHANISMS (PART.1)
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Alcohol Conversion Summary:
ORGANIC - CAREY 10E
CH. 5 - ALCOHOLS AND ALKYL HALIDES: INTRODUCTION TO REACTION MECHANISMS (PART.1)
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