More About the Families in Group II The families in Group II all have an electronegative atom or group that is attached to an sp3 carbon. 5- כוהלים ואתרים

Strongly Basic Leaving Groups Cannot Be Displaced 5- כוהלים ואתרים

Acid Converts the Poor Leaving Group into a Good Leaving Group Alcohols have to be “activated” before they can react. Only weakly basic nucleophiles can be used. Strongly basic nucleophiles would react with the proton. 5- כוהלים ואתרים

Primary and Secondary alcohols require heat; tertiary alcohols do not. Converting Alcohols to Alkyl Halides Primary and Secondary alcohols require heat; tertiary alcohols do not. 5- כוהלים ואתרים

The Reactions of Secondary and Tertiary Alcohols with Hydrogen Halides are SN1 Reactions 5- כוהלים ואתרים

An SN1 Reaction Creates a Carbocation Intermediate, So Watch Out for Carbocation Rearrangements 5- כוהלים ואתרים

Ring Expansion 5- כוהלים ואתרים

The Reactions of Primary Alcohols with Hydrogen Halides are SN2 Reactions Recall that Br– is a good nucleophile in a protic solvent. Alcohols undergo SN1 reactions unless they would have to form a primary carbocation. 5- כוהלים ואתרים

Cl– is the Poorest Nucleophile of the Halide Ions ZnCl2 increases the rate of the reaction by creating a better leaving group than water. רשות 5- כוהלים ואתרים

Why is It Important to Be Able to Convert Alcohols to Alkyl Halides? Alcohols are readily available but unreactive. Alkyl halides are less available but reactive and can be used to synthesized a wide variety of compounds. 5- כוהלים ואתרים

phosphorus tribromide, phosphorus trichloride, thionyl chloride Other Methods to Convert Alcohols into Alkyl Halides phosphorus tribromide, phosphorus trichloride, thionyl chloride 5- כוהלים ואתרים

The Mechanism for the Reaction with PBr3 or PCl3 רשות A bromophosphite (chlorophosphite) group is a better leaving group than a halide ion. Pyridine is the solvent and acts as a base. 5- כוהלים ואתרים

The Mechanism for the Reaction with SOCl2 רשות A chlorosulfite group is a better leaving group than a halide ion. Pyridine is the solvent and acts as a base. 5- כוהלים ואתרים

Converting Alcohols to Alkyl Halides 5- כוהלים ואתרים

Primary and Secondary Alcohols Can Be Activated by Being Converted to Sulfonate Esters 5- כוהלים ואתרים

A Sulfonic Acid is a Strong Acid 5- כוהלים ואתרים

Common Sulfonyl Chlorides tosyl chloride = TsCl 5- כוהלים ואתרים

The Mechanism רשות 5- כוהלים ואתרים

A Sulfonate Ester Reacts with Nucleophiles 5- כוהלים ואתרים

Dehydration of an Alcohol Dehydration of an alcohol is an elimination reaction. 5- כוהלים ואתרים

Dehydration is a Reversible Reaction To prevent the alkene from adding water and reforming the alcohol, the water is removed as it is formed. 5- כוהלים ואתרים

Dehydration of Secondary and Tertiary Alcohols are E1 Reactions 5- כוהלים ואתרים

Dehydration The major product is the more stable alkene. 5- כוהלים ואתרים

The More Stable Alkene Has the More Stable Transition State Leading to Its Formation 5- כוהלים ואתרים

Tertiary Alcohols are the Easiest to Dehydrate The rate of dehydration reflects the ease of carbocation formation. 5- כוהלים ואתרים

An E1 Reaction Creates a Carbocation Intermediate, So Watch Out for Carbocation Rearrangements 5- כוהלים ואתרים

Dehydration of a Primary Alcohol is an E2 Reaction Both E2 and SN2 products are obtained. Alcohols undergo E1 reactions unless they would have to form a primary carbocation. 5- כוהלים ואתרים

Dehydration The major product is the stereoisomer with the largest groups on opposite sides of the double bond. 5- כוהלים ואתרים

Oxidation of Secondary Alcohols 5- כוהלים ואתרים

Oxidation of Primary Alcohols 5- כוהלים ואתרים

Tertiary Alcohols Cannot Be Oxidized to a Carbonyl Compound 5- כוהלים ואתרים

Oxidation by Hypochlorous Acid (HOCl) 5- כוהלים ואתרים

The Mechanism רשות 5- כוהלים ואתרים

Alcohols and Ethers Have Similar Leaving Groups Alcohols and ethers have to be “activated” before the compounds can react. 5- כוהלים ואתרים

The Leaving Group of an Ether Can Be Activated by Protonation 5- כוהלים ואתרים

The Mechanism If a relatively stable carbocation is formed when ROH leaves, it will be an SN1 reaction. 5- כוהלים ואתרים

it will be an SN2 reaction. The Mechanism If a relatively stable carbocation would not be formed when ROH leaves, it will be an SN2 reaction. Ethers undergo SN1 reactions unless they would have to form a primary carbocation. 5- כוהלים ואתרים

Nomenclature of Epoxides 6-אלקנים

Epoxides are More Reactive Than Ethers Because of Ring Strain 5- כוהלים ואתרים

The Acid-Catalyzed Mechanism 5- כוהלים ואתרים

If the Epoxide is Not Symmetrical, Which Carbon Does the Nucleophile Attack? The nucleophile attacks the more substituted ring carbon. 5- כוהלים ואתרים

Under Acidic Conditions the Nucleophile Attacks the More Substituted Ring Carbon 5- כוהלים ואתרים

Under Neutral or Basic Conditions the Nucleophile Attacks the Less Substituted Carbon 5- כוהלים ואתרים

The Conditions Determine the Site of Nucleophilic Attack 5- כוהלים ואתרים

Using Epoxides in Synthesis 5- כוהלים ואתרים

ריאגנט גריניאר Grignard Reagents: Alkylmagnesium halide, RMgX, produced from reaction of alkyl halides, RX, with magnesium metal in ether or tetrahydrofuran (THF) solvent The carbon atom is both nucleophilic and basic 5- כוהלים ואתרים

ריאגנט גריניאר They react with weak acids such as H2O, ROH, RCO2H, and RNH2 to abstract a proton and yield hydrocarbons Since hydrocarbons are weak acids, with pKa’s in the range of 44 to 60, carbon anions are very strong bases Because even trace amounts of moisture can destroy an organometallic compound, it is important that all reagents be dry when organometallic compounds are being synthesized and when they react with other reagents 5- כוהלים ואתרים

מחמצנים ומחזרים ביולוגיים 5- כוהלים ואתרים

מנגנון [רשות] 5- כוהלים ואתרים

An Unusual Antibiotic[העשרה] 5- כוהלים ואתרים