Chapter 9.3 – Alkenes and alkynes - highschoolscienceblog



Organic ChemistryChapter 9.3 – Alkenes and alkynesAlkenes and alkynes are carbon chains that contain a double or a triple bond. Since they contain additional bonds they cannot hold as many hydrogens. If there is one double bond (alkene), they can hold two less than an alkane. If there is one triple bond (alkyne), they can hold four less hydrogens. Alkyne is also known as acetyleneThe following are the general equations for alkane, alkenes, and alkynes.An alkane has the maximum amount of hydrogens available to bond. This make them saturated Hydrocarbons. Alkenes and alkynes are unsaturated hydrocarbons due to the fact they can hold less hydrogens than the maximumChapter 9.3 – Naming alkenes and alkynesWith alkenes and alkynes there are a couple of changes to naming to account for the bond type and position.Rules for naming: Find the longest continuous carbon chain CONTAINING THE DOUBLE OR TRIPLE BOND to get the prefix (meth-, eth-, prop-, etc)As long as all the bonds between the carbons are single, then the ending is –ane. If there is a double bond, the ending becomes –ene. If there is a triple bond, the ending becomes –yne.The numbering for the bond position is more relevant than the alkyl brances so the counting begins from the side closest to the double or triple bond. The numbering is put between the prefix for the number of carbons and the –ene or –yne ending. NO number is needed for eth- or prop-If there is a branch off the main chain it must also be named. This is called an Alkyl group. A one carbon long alkyl group is methyl, a two carbon long one is ethyl and a three carbon one is a propyl. The position and the number of these branches must be clear as they can also create different isomers.If there is only one branch no prefix is needed in front of the alkyl. If there are two or more…(di-, tri-, tetra-, etc)The position of the branches must be named as well by putting a number in front of the Alkyl prefix. The numbers should always start as low as possible, so check both directions on the chain.If there is more than one type of branch (ex a methyl and an ethyl) they are placed alphabetically.Try these:Cycloalkenes and cycloalkynesFor carbon chains in a loop, if they contain at least 1 double or triple bond the numbering begins from the double or triple bond.All of these alkane, alkene, alkyne and cycloalkane, cycloalkane, cycloalkynes are part of a family called aliphatic hydrocarbons. The next section we cover will discuss aromatic hydrocarbons.Try these:Practice: Page 380 #1,4,5,6,7,9,11Ethane Cracking:Ethene is very important in many chemical products, such as polyethene which is one of the most common forms of plastic created in the world with tons being produced every year. One of the ways to produce ethane is called ethane cracking where saturated ethane and heat react to break off 2 hydrogens atoms and create ethane.359664020701000When ethane is combined in a very large chain of plastic it is called polyethene (polyethylene). This is done by the double bonds splitting and allowing it to attach to other ethenes that have broken their double bond as well. ................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download