Organic Chemistry (CHM 222) Chapter 9

Alcohols, ethers, and epoxides.

True (A)

<p>Alcohols are classified according to the number of alkyl groups attached to the carbon bearing the -OH group. They are categorized as primary (1°), secondary (2°), or tertiary (3°) alcohols.</p> Signup and view all the answers

<p>Change the -e ending of the parent alkane to the suffix -ol. Number the carbon chain to give the OH group the lowest number.</p> Signup and view all the answers

<p>Diols (B)</p> Signup and view all the answers

<p>The Williamson Ether Synthesis is a method used to synthesize unsymmetrical ethers by reacting an alkoxide with a less hindered alkyl halide.</p> Signup and view all the answers

<p>All of the above (D)</p> Signup and view all the answers

<p>Alcohols exhibit stronger intermolecular hydrogen bonding due to the presence of the -OH group, contributing to their higher polarity compared to ethers and epoxides.</p> Signup and view all the answers

<p>Alcohols have a better leaving group. (D)</p> Signup and view all the answers

<p>The dehydration of alcohols is primarily a β-elimination reaction, where an -OH group and a hydrogen atom are removed from adjacent carbon atoms to form a new carbon-carbon double bond (an alkene).</p> Signup and view all the answers

<p>True (A)</p> Signup and view all the answers

<p>Both A and B (B)</p> Signup and view all the answers

<p>Zaitsev's Rule states that the more substituted alkene is the major product when alkene formation is possible during alcohol dehydration.</p> Signup and view all the answers

<p>True (A)</p> Signup and view all the answers

<p>SN2 (D)</p> Signup and view all the answers

<p>Pyridine acts as a base in this reaction, helping to deprotonate the alcohol and facilitate the formation of a good leaving group (tosylate).</p> Signup and view all the answers

<p>True (A)</p> Signup and view all the answers

<p>Reaction with a strong acid (B)</p> Signup and view all the answers

<p>True (A)</p> Signup and view all the answers

<p>Nucleophilic attack occurs on the less substituted carbon of the epoxide ring, opening it and forming a new C-Nu bond. This is typically an SN2 reaction.</p> Signup and view all the answers

<p>All of the above (D)</p> Signup and view all the answers

<p>Acids containing a nucleophilic atom (Z) open epoxide rings through a two-step sequence: 1) Protonation of the epoxide oxygen to form a good leaving group, and 2) Backside backside attack by the nucleophile (Z).</p> Signup and view all the answers

<p>The HCl will protonate the epoxide oxygen, leading to a more stable carbocation intermediate on the more substituted carbon. The chloride anion will then attack this carbocation from the back side (SN2 mechanism), forming a 2-haloalcohol. Only one product will form in this reaction because the transition state where the chloride anion attacks the more substituted carbon is more stable.</p> Signup and view all the answers

<p>Alcohols and ethers often require conversion of their oxygen atoms into better leaving groups to undergo various reactions. These conversions utilize strong acids and bases, and the reactions often proceed via SN1, SN2, or elimination pathways. Understanding stereochemistry, regiochemistry, and major/minor product rules is essential for predicting the outcomes of reactions.</p> Signup and view all the answers

A compound containing a hydroxy group (OH) bonded to an sp3 hybridized carbon atom, represented as R-OH.

Classified based on the number of alkyl groups attached to the carbon bearing the OH group.

Compounds where two alkyl groups are bonded to an oxygen atom.

Ethers where the oxygen atom is part of a 3-membered ring. More reactive than other ethers due to angle strain.

Changing the ending of the parent alkane to ‘-ol’. The carbon chain is numbered so that the OH group gets the lowest number.

Alcohols with two hydroxy groups (e.g., 1,2-ethanediol).

Alcohols with three hydroxy groups (e.g., glycerol).

Simple ethers are named by listing the alkyl groups bonded to the oxygen in alphabetical order, followed by the word “ether”. Symmetrical ethers use a prefix “di-”.

Cyclic ethers have an oxygen atom included in the ring structure.

Epoxides can be named using three methods: epoxyalkanes, oxiranes, or alkene oxides.

This method uses the alkane chain or ring where the oxygen is attached and adds “epoxy” before its position.

Epoxides are also named by mentally replacing the oxygen with a double bond, naming the alkene, and adding “oxide”.

Alcohols form intermolecular hydrogen bonds due to the electronegativity of oxygen, making them more polar than ethers and epoxides.

This property, governed by the balance of intermolecular forces (hydrogen bonding vs. Van der Waals), influences the solubility of alcohols and ethers in water.

Both alcohols and ethers can be formed from nucleophilic substitution reactions, where the nucleophile attacks a carbon attached to a leaving group.

This method produces unsymmetrical ethers by reacting an alkoxide with a less hindered alkyl halide.

Alcohols react with bases like NaOH to form alkoxides via an acid-base reaction.

Halohydrins contain both a hydroxy group and a halogen on adjacent carbons. An intramolecular Williamson ether synthesis forms epoxides by the reaction of halohydrins with NaOH.

OH group is a poor leaving group in alcohols. It must be converted into a better leaving group for nucleophilic substitution to occur.

Alcohols can be protonated with strong acids to allow water to act as a leaving group, leading to substitution and elimination reactions.

The dehydration of alcohols is an elimination reaction where OH and H are removed from the α and β carbons, respectively.

Strong acids like H2SO4, TsOH, or reagents like POCl3 in the presence of a base are needed to induce dehydration.

More substituted alcohols react faster due to the stability of the carbocation formed during dehydration.

Dehydration follows Zaitsev's rule, leading to the formation of the more substituted alkene as the major product.

The formation of a more stable carbocation from a less stable one by the shift of a hydrogen or alkyl group.

A 1,2-shift is a two-electron movement that shifts a hydrogen or alkyl group and the positive charge.

A rearrangement involving the movement of an alkyl group from one carbon to its adjacent carbon.

A rearrangement involving the movement of a hydrogen atom from one carbon to its adjacent carbon.

POC3 converts the −OH group into a good leaving group (P-complex) for the dehydration reaction to proceed via an E2 mechanism.

Ethers are not as reactive as alcohols due to the poor leaving group present in their structure.

Epoxides undergo reactions readily due to the ring strain present in the three-membered ring structure.

Epoxides react with strong nucleophiles and acids, opening the three-membered ring.

Strong nucleophiles open the epoxide ring in a two-step reaction with an SN2 mechanism.

Acids containing a nucleophile also open epoxide rings, involving protonation of the epoxide oxygen followed by nucleophilic attack.

Trans-1,2-disubstituted cycloalkanes are formed from epoxides fused to rings by opening the epoxide ring with acids.

The reaction of alcohols and ethers involves conversion of the oxygen into a better leaving group, followed by substitution and elimination reactions.