Chapter 12 Alkenes, Alkynes, and Aromatic Compounds Compounds with multiple bonds The most important compound with a triple bond is ethyne also known as acetylene; it is used in the oxy acetylene torch. Bombykol, is another natural product that contains double bonds. We will examine the structure of these materials shortly

Compounds of carbon and hydrogen with less tha 2n+ 2 hydrogens other than cyclic hydrocarbons Is there any other way of satisfying the octet for carbon in a molecule with a formula C 2 H 4 or C 2 H 2 ? :: How many groups around each C? (bonding electrons are not considered to be a group) 3 What’s the geometry?triangular How about C 2 H 2 ?  How many groups around each C?2 What’s the geometry?linear

ethene or ethylene What does ethylene have to do with fruit?

A systematic way of naming alkenes and identifying identical structures 1.Locate the longest carbon chain in the molecule that contains the double bonds: this identifies the parent alkene 2. Identify the points of branching and count the number of carbons in each branch; name the alkyl branches in the normal way: methyl, ethyl Give the double bond the lowest number 4. Identify any stereochemistry parent: groups: location: 4 carbons: butene 2 carbons: ethyl double bond at position 1; ethyl at 2 2-ethyl-1-buteneno stereochemistry to describe

All these formulas for butane are identical because of rapid rotation about C-C bonds no, rotation about C=C bonds does not occur Are these two compounds the same? If the two groups are on the same side of the double bond, use cis On opposite sides, use trans

parent: cyclohexane groups: ethyl, chloro location: 1, 3 The solid wedge is used to denote a group sticking out of the plane of the screen A dotted wedge is used to denote a group sticking out of the plane of the screen Two groups with the same relative orientation is called cis Two groups with the opposite relative orientation is called trans

Naming compounds with double and triple bonds generic names alkane alkene alkyne ethane ethene or ethylene ethyne or acetylene cis 2-butene trans 2-butene 2-butyne 1-butene 1-butyne

Name the following: parent: groups: location: nonene methyl, double bond 3-methyl, 4-double bond trans 3-methyl-4-nonene shorthand notation parent: groups: location: cyclohexene methyl 1, 3 or 1,2? 3-methyl-1-cyclohexene or 1-methyl-2-cyclohexene stereochemistry:trans

A pheromone is a chemical messenger emitted by insects in minute quantities. Bombykol is emitted by the silkworm moth to attract other moths and has one cis and one trans double bond To name this compound we need to know how to name a compound with 16 carbon atoms How to name compounds with more than one double bond How to name alcohols and how to designate “stereochemistry” (the arrangement of groups in space: 16 C: hexadecane 2 double bonds diene alcohol: drop the last e and add ol stereochemistry: cis and trans (CH 2 ) 7 means 7 CH 2 groups in a row trans10, cis 12-hexadecadien-1-ol

Name the following: cis-1,2-Dibromoethene trans-2-Butene 1,1-Dichloropropene parent: groups: location stereochemistry : parent: groups: location: stereochemistry: parent: groups: location: stereochemistry: ethene bromo 1,2 cis butene double bond 2 trans propene chloro 1,1 none

parent: groups: location stereochemistry: parent: groups: location stereochemistry:

Dill Anethum graveolens (Umbelliferae) Dill is a thin, annual originating in the Middle East. Since recorded history it has been cultivated as a medicinal and aromatic herb. It was spread through Europe by way of the monasteries. The picture on the left shows a 'broad-leafed' variety, the original type has completely thready leaflets. The fresh dill leaves and flowers contain an essential oil whose main component is (-)-alpha-phellandrene (ca. 60 %). 2 -methyl-5-isopropyl-1,3-cyclohexadiene

Draw structures for the following compounds: 1-hexyne 2-methyl-1,7-octadiene 1,2-propadiene

Compounds of carbon with multiple bonds to other elements If the carbon of the carbonyl group is attached to two other carbon atoms the compound is called a ketone, An aldehyde contains a carbonyl group (C=O), which is a carbon atom with a double bond to an oxygen atom, attached to at least one hydrogen. Oxygen double bonded to carbon is called a carbonyl group (C=O)

Carboxylic acids contain the carboxyl group, which is a carbonyl group attached to a hydroxyl group. In an ester, the hydrogen on oxygen is replaced by a carbon atom. acetic acid or ethanoic acid O O A nitrogen attached to a carbonyl group is called an amide; the other two groups attached to nitrogen can be either both carbons, hydrogens or a mix of both carbon and hydrogen N

A few reactions of unsaturated compounds: Adding H 2 to double bonds in vegetable oils produces compounds with higher melting points solids at room temperature, such as margarine, soft margarine, and shortening. This makes them less reactive and less prone to become rancid; rancidness is due to reaction of the double bonds with oxygen +H 2 (catalyst) unsaturated triglyceride saturated triglyceride butyric acid

Polymers are large, long-chain molecules; they are found in nature, including cellulose in plants, starches in food, and proteins and DNA in the body; they are also made synthetically, such as polyethylene and polystyrene, Teflon, and nylon they are made up of small repeating units called monomers that are often alkenes

Teflon Polypropylene Polyvinyl chloride

Recycling is simplified by using codes found on plastic items.

Aromatic Compounds Different ways of representing the molecule benzene Molecules that contain a benzene ring are often referred to as aromatic compounds, originally because of their odor

methylbenzene (toluene) aminobenzene (aniline) hydroxybenzene (phenol)

salicylic acid methyl salicylate 2-hydroxybenzoic acid methyl 2-hydroxybenzoate acetosalicylic acid benzoic acid 1-methyl,2,4,6-trimethylbenzene benzaldehyde 4-hydroxy-3- methoxybenzaldehyde

naphthalene 1,4-dichlorobenzene benzo[a]pyrene