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Hydrocarbons

Hydrocarbons. SCH4U0. Organic Molecules. Organic molecules contain several different groups that convey different chemical and physical properties to the molecules These groups are called “functional groups”. Hydrocarbons. We will start discussing the simplest functional groups;

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Hydrocarbons

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  1. Hydrocarbons SCH4U0

  2. Organic Molecules • Organic molecules contain several different groups that convey different chemical and physical properties to the molecules • These groups are called “functional groups”

  3. Hydrocarbons • We will start discussing the simplest functional groups; • Those involving only carbon and hydrogen • Compounds that involve only carbon and hydrogen are called hydrocarbons

  4. Aliphatic Hydrocarbons • Aliphatic hydrocarbons consist of three main groups • Alkanes – Contain only C – C and C – H single bonds • Alkenes – Contain C – C double bonds • Alkynes – Contain C – C triple bonds • These can be straight-chain or cyclic Alkanes Alkynes Alkenes

  5. Aromatic Hydrocarbons • Aromatic hydrocarbons have very unique characteristics • Very unreactive • Contain 4n+2 pi electrons • Are totally flat and cyclic • Have conjugated pi bonds throughout the whole molecule Eg: Benzene Naphthalene

  6. Alkanes • Alkanes are non-polar • MP/BP depends mainly on surface area • To name alkanes we use Greek prefixes to denote how many carbon atoms there are • We use the suffix “-ane” to denote that the molecule is an alkane and doesn’t contain any other functional groups butane hexane

  7. Cyclic Alkanes • When the alkane is joined into a ring, we call it a cyclic alkane • To name these compounds, we name them as alkanes with the prefix “cyclo-” in front of the normal name cyclopentane cyclohexane

  8. Branches • Some molecules have branched chains of carbons • We call these substituents • When naming molecules like this we follow two main rules • The longest chain of carbons is the main compound • Any branches are named as substituents • Alkane substituent groups are called alkyl groups • They get a “-yl” suffix and are named before the main compound name

  9. Branches • Example: • This compound has a main chain of 6 carbons, with a branch containing 2 carbons • The carbon atoms in the main chain are numbered so that the substituent gets the smallest number possible 1 5 3 2 4 6 3- ethyl hexane

  10. Multiple Groups • If there are multiple substituents; • They are listed alphabetically • They get Latin prefixes (di, tri, tetra, etc) to denote multiple copies of the same group 2,2- dimethyl butane cyclo pentane 4- ethyl -2- methyl heptane 1,2- diethyl

  11. Alkenes • Alkenes are hydrocarbons that contain C – C double bonds • When naming, they get the “-ene” suffix • The position of the double bond must also be numbered and placed directly in front of the suffix • Multiple double bonds get di/tri prefixes as well • Cis/trans labels also apply pent -2- ene trans- but -1,3- di ene but -1- ene Old method: 1,3 - butadiene Old method: trans – 2 – pentene Old method: 1 - butene

  12. Alkenes • Name the following molecules • Draw the following molecules cyclopent-1,3-diene Or 1,3-cyclopentadiene 4-ethyl-2,5-dimethylhex-2-ene Or 4-ethyl-2,5-dimethyl-2-hexene 4,5,5-triethyl-trans-hept-3-ene 3-methylcyclohexene

  13. Alkynes • Alkynes contain C – C triple bonds • When naming, use the “-yne” suffix • All other rules are the same as for alkenes • Note: the bond angle in a triple bond is 180º. This must be shown in your diagrams • Also, there are no cis/trans isomers, nor cyclic alkynes oct -1,7- di yne pent -1- yne Old method: 1,7 - octadiyne Old method: 1 - pentyne

  14. Alkynes • Name the following molecules • Draw the following molecules 2,5-dimethylhex-3-yne 5-ethylhept-1,3-diyne 3-propylhex-1-yne 3-cyclobutyl-2-methylnon-4-yne

  15. Special Hydrocarbon Substituents • Benzene • As a substituent, the benzene group is called “phenyl” 4-phenylhept-1-ene • Iso-alkyl groups • If an alkyl group contains the following group, it gets an “iso-”prefix 3-isopropylpentane isobutylcyclopentane

  16. Primary, Secondary, and Tertiary • If an alkyl group is connected at the terminal carbon, it is sometimes labelled with an “n-” n-butylcyclopentane • If an alkyl group is connected at a carbon that has two other carbons attached to it (this is called a secondary carbon) • It is labelled with an “s-” or “sec-” • If an alkyl group is connected at a carbon that has three other carbons attached to it (this is called a tertiary carbon) • It is labelled with a “t-” or “tert-” sec-butylcyclopentane t-butylcyclopentane

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