CHEM 127 Lecture Notes - Lecture 1: Epoxide, Molecular Geometry, Ring Strain

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26 May 2018

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Chemistry Chapter 9

9.1

Alcohols, ethers, and epoxides are three functional groups that contain carbon-oxygen σ bonds

- Alcohols contain a hydroxyl group (OH group) bonded to an sp3 hybridized carbon atom.

- Alcohols are also classified as primary (1o), secondary (2o), or tertiary (3o) based on the

number of carbon atoms bonded to the carbon with the OH group.

- Compounds having a hydroxyl group on an sp2 hybridized carbon atom – enols and phenols –

undergo different reactions than alcohols.

- Enols have an OH group on a carbon of a C-C double bond.

- Phenols have an OH group on a benzene ring

- Ethers have two alkyl groups bonded to an oxygen atom.

- An ether is symmetrical if the two alkyl groups are the same, and unsymmetrical if

they are different

- Both alcohols and ethers are organic derivatives of H2O, formed by replacing one or both of the

hydrogens on the oxygen atom by R groups

- Epoxides are ethers having the oxygen atom in a three-membered ring.

- Epoxides are also called oxiranes

9.2

Alcohols, ethers, and epoxides each contain an oxygen atom surrounded by two atoms and two

nonbounded electron pairs, making the O atom tetrahedral and sp3 hybridized.

- Because only two of the four groups around O are atoms, alcohols and ethers have a bent shape

like H2O

- The bond angle around the O atom in an alcohol or ether is similar to the tetrahedral

bond angle of 109.5o.

-In contrast, the C-O-C bond angle of an epoxide must be 60o, a considerable

deviation from the tetrahedral bond angle.

- For this reason, epoxides have angle strain, making them much more reactive

than other ethers

- Because oxygen is much more electronegative than carbon or hydrogen, the C-O and O-H

bonds are all polar, with the O atom electron rich and the C and H atoms electron poor.

9.3

Naming Alcohols

- In the IUPAC system, alcohols are identified by the suffix –ol

1) Find the longest carbon chain containing the carbon bonded to the OH group

2) Number the carbon chain to the give the OH group the lower number, and apply all

other rules of nomenclature

- When an OH group is bonded to a ring, the ring is numbered beginning with the OH group.

Because the functional group is always at C1, the “1” is usually omitted from the name. The ring

is then numbered in a clockwise or counterclockwise fashion to give the next substituent the

lower number

- Common names are often used for simple alcohols. To assign a common name:

- Name all the carbon atoms of the molecule as a single alkyl group

- Add the word alcohol, separating the words with a space

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Document Summary

Alcohols, ethers, and epoxides are three functional groups that contain carbon-oxygen bonds. Alcohols are also classified as primary (1o), secondary (2o), or tertiary (3o) based on the number of carbon atoms bonded to the carbon with the oh group. Enols have an oh group on a carbon of a c-c double bond. Phenols have an oh group on a benzene ring. An ether is symmetrical if the two alkyl groups are the same, and unsymmetrical if they are different. Alcohols contain a hydroxyl group (oh group) bonded to an sp3 hybridized carbon atom. Compounds having a hydroxyl group on an sp2 hybridized carbon atom enols and phenols undergo different reactions than alcohols. Ethers have two alkyl groups bonded to an oxygen atom. Both alcohols and ethers are organic derivatives of h2o, formed by replacing one or both of the hydrogens on the oxygen atom by r groups. Epoxides are ethers having the oxygen atom in a three-membered ring.

Related Questions

Part F: some functional groups

Classify each of the following statements as true or false:

a) To be classified as organic, a compound must be or have been part of a living organism.

b) Carbon atoms normally form four bonds in organic compounds.

c) Only an unsaturated hydrocarbon can engage in an addition reaction.

d) Members of a homologous series differ by a distinct structural unit.

e) Alkanes, alkenes, and alkynes are unsaturated hydrocarbons.

f) Alkyl groups are a class of organic compounds.

g) Isomers have the same molecular formulas but different structural formulas.

h) Cis-trans isomerism appear among alkenes but not alkynes.

i) All aliphatic hydrocarbons are unsaturated.

j) Aromatic hydrocarbons have a ring structure.

k) An alcohol has an alkyl group bonded to an oxygen atom, and an ether has two.

l) Carbonyl groups are found in alcohols and aldehydes.

m) An ester is an aromatic carbon made from the reaction of an alcohol and a carboxylic acid.

n) An amine has one, two, or three alkyl groups substituted for hydrogens in an ammonia molecule.

o) An amide has the structure of a carboxylic acid except that replaces OH in the carboxyl group.

p) A peptide linkage series arises when a water molecule forms from a hydrogen from the of one amino acid molecule an from an another amino acid molecule.