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Ch. 12 J.C. Rowe

Windsor University School of Medicine. Introduction to organic chemistry Scientific research consists in seeing what everyone else has seen, but thinking what no one else has thought.  A. Szent-Gyorgyi. Ch. 12 J.C. Rowe. Catenation (chains or ring structures).

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Ch. 12 J.C. Rowe

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  1. Windsor University School of Medicine Introduction to organic chemistryScientific research consists in seeing what everyone else has seen, but thinking what no one else has thought. A. Szent-Gyorgyi Ch. 12 J.C. Rowe

  2. Catenation (chains or ring structures) • Organic chemistry is the study of carbon compounds. • Organic compounds are essential for life processes & for the growth of plants & animals

  3. Unbranched vs. Branched “C”chains UNBRANCHED “C” CHAIN BRANCHED “C” CHAIN

  4. RINGS “C” CHAIN • Cyclopropane C3H6 • Cyclobutane C4H8 • Cyclopentane C5H10 • Cyclohexane C6H12

  5. Substituted Carbon chains • Hydrogen in organic compound can be replaced by a nonmetal such as nitrogen, chlorine, fluorine, bromine, oxygen & sulfur

  6. Condensed vs. fully displayed formulae

  7. Saturated compounds • An organic compound that contains only carbon-carbon (C—C) single bonds throughout its entire structure is called a saturated compound

  8. Unsaturated compounds • An organic compound that contains at least one multiple bond between a pair of carbon at some point within the chain is called unsaturated compound

  9. Nomenclature of Organic Compound ALKANES ALKYL ALKENES ALCOHOLS CARBOXYLIC ACIDS ESTERS

  10. ALKANE (CnH2n+2; n≥1) • Alkanes are the simplest family of hydrocarbons - compounds containing carbon and hydrogen only. They only contain carbon-hydrogen bonds and carbon-carbon single bonds. • You can work out the formula of any of them using: CnH2n+2

  11. The first six AlkanesCnH2n+2 are: • Methane CH4 • Ethane C2H6 • Propane C3H8 • Butane C4H10 • Pentane C5H12 • Hexane C6H14

  12. Isomerism • All the alkanes with 4 or more carbon atoms in them show structural isomerism. This means that there are two or more different structural formulae that you can draw for each molecular formula. • For example, C4H10 could be either of these two different molecules: butane  and  2-methylpropane.

  13. Cycloalkanes (CnH2n) • Cycloalkanes again only contain carbon-hydrogen bonds and carbon-carbon single bonds, but this time the carbon atoms are joined up in a ring.

  14. Cyloalkane Cont’d. • The smallest cycloalkane is cyclopropane. • If you count the carbons and hydrogens, you will see that they no longer fit the general formula CnH2n+2. By joining the carbon atoms in a ring, you have had to lose two hydrogen atoms. • The general formula for a cycloalkane is CnH2n.

  15. ALKYL • An alkyl group is a group such as methyl, CH3, or ethyl, CH3CH2. These are groups containing chains of carbon atoms which may be branched. • Alkyl groups are given the general symbol R.

  16. ALKENE (CnH2n ; n≥2) • Alkenes are a family of hydrocarbons (compounds containing carbon and hydrogen only) containing a carbon-carbon double bond. The first two are: • Ethene C2H4 • Propene C3H6 • You can work out the formula of any of them using: CnH2n

  17. Isomerism in the alkenes • Structural isomerism All the alkenes with 4 or more carbon atoms in them show structural isomerism. This means that there are two or more different structural formulae that you can draw for each molecular formula.

  18. C4H8 with three structural isomers:

  19. Isomerism in the alkenes Cont’d. • Geometric (cis-trans) isomerism • The carbon-carbon double bond doesn't allow any rotation about it. That means that it is possible to have the CH3 groups on either end of the molecule locked either on one side of the molecule or opposite each other. • These are called cis-but-2-ene (where the groups are on the same side) or trans-but-2-ene (where they are on opposite sides).

  20. Cis vs. Trans alkenes • Cis-but-2-ene is also known as (Z)-but-2-ene; trans-but-2-ene is also known as (E)-but-2-ene.

  21. Alkenes cis-Alkene trans-Alkene

  22. ALCOHOLS • Alcohols are compounds in which one or more hydrogen atoms in an alkane have been replaced by an -OH group. • We will only look at compounds containing one -OH group.

  23. The different kinds of alcohols • Alcohols fall into different classes depending on how the -OH group is positioned on the chain of carbon atoms. • (1°) alcohol; (2°) alcohol; (3°) alcohol • There are some chemical differences between the various types.

  24. (1°) alcohol; (2°) alcohol; (3°) alcohol • The easy way to work it out is the number of carbon atoms bonded to the COH group. A primary alcohol has 0 or 1 carbon on the COH. The secondary alcohol has 2 carbons and the tertiary alcohols have got 3 carbon atoms bonded to the C-OH.

  25. Primary alcohols R-CH2- • In a primary (1°) alcohol, the carbon which carries the -OH group is only attached to one alkyl group.

  26. Secondary alcohols R2CH- • In a secondary (2°) alcohol, the carbon with the -OH group attached is joined directly to two alkyl groups, which may be the same or different.

  27. Tertiary alcohols R3C- • In a tertiary (3°) alcohol, the carbon atom holding the -OH group is attached directly to three alkyl groups, which may be any combination of same or different.

  28. CARBOXILIC ACIDS • Carboxylic acids contain a -COOH group • Carboxylic acids are compounds which contain a -COOH group. • We will look at compounds where the -COOH group is attached either to a hydrogen atom or to an alkyl group.

  29. Examples of carboxylic acids • The name counts the total number of carbon atoms in the longest chain - including the one in the -COOH group. If you have side groups attached to the chain, notice that you always count from the carbon atom in the -COOH group as being number 1.

  30. ESTERS • Esters are derived from carboxylic acids. • A carboxylic acid contains the -COOH group, and in an ester the hydrogen in this group is replaced by a hydrocarbon group of some kind. • This could be an alkyl group like methyl or ethyl, or one containing a benzene ring like phenyl.

  31. A common ester - ethyl ethanoate • The most commonly discussed ester is ethyl ethanoate. In this case, the hydrogen in the -COOH group has been replaced by an ethyl group. The formula for ethyl ethanoate is:

  32. A few more esters • Notice that the acid is named by counting up the total number of carbon atoms in the chain - including the one in the -COOH group. So, for example, CH3CH2COOH is propanoic acid, and CH3CH2COO is the propanoate group.

  33. Albert Einstein Anyone who doesn't take truth seriously in small matters cannot be trusted in large ones either. 

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