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by dr. siham lahsasni

. . . Aliphatic. Aromatic. . . straight. Ring. Alkanes, Alkenes

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by dr. siham lahsasni

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    1. By Dr. Siham Lahsasni

    2. Hydrocarbons : Carbon and Hydrogen atoms

    3. Alkanes : CnH2n+2

    4. Classes of carbon and Hydrogen Primary carbon : CH3-R Secondary carbon : R-CH2-R Tertiary carbon : (R)2-CH-R Quaternary carbon: (R)4-C Hydrogens are also referred to as 1ş, 2ş or 3ş according to the type of carbon they are bonded to.

    8. Structural Isomerism

    9. Pentane, C5H12 has three chain isomers.

    10. Alkyl groups Alkyl groups are named by dropping the -ane suffix of the alkanes and adding the suffix -yl. Methane becomes a methyl group, ethane an ethyl group, etc.

    12. IUPAC system of nomenclature Find and name the longest continuous carbon chain. Identify and name groups attached to this chain. Number the chain consecutively, starting at the end nearest a substituent group. Designate the location of each substituent group by an appropriate number and name. Assemble the name, listing groups in alphabetical order. The prefixes di, tri, tetra etc., used to designate several groups of the same kind, are not considered when alphabetizing. Halogen substituent's are easily accommodated, using the names: fluoro (F-), chloro (Cl-), bromo (Br-) and iodo (I-) also (-NH2) amino, (-NO2) nitro…

    13. 1- Locate the longest continuous chain of carbon atoms; this chain determines the parent name for the alkane. Sometimes, you may need to go around corners and zigzag to find the longest (parent) chain. (the parent chain is in blue): If the parent chain for example has 6 carbon atoms, therefore, it is a derivative of hexane and if it has 4 carbon atoms it is derivative of butane and so on . 13

    14. 2- Number the longest chain beginning with the end of the chain nearer to the substituent. 14

    15. 3- Use the numbers obtained by application of rule 2 to designate the location of the substituent group. 15

    16. 4. When two or more substituents are present, give each substituent a number corresponding to its location on the longest chain. 16

    17. 5) When two or more substituents are identical, indicate this by the use of the prefixes di-, tri-, tetra-, and so on. 17

    18. 6) When two substituents are present on the same carbon, use the number twice. 18

    19. 7. When two chains of equal length compete for selection as the parent chain, choose the chain with the greater number of substituents. 19

    20. 8. When branching occurs at an equal distance from both ends of the longest chain, choose the name that gives the lower number at the first point of difference. 20

    21. Drawing alkanes

    22. Physical Properties Methane, ethane, propane, and butane are gases; pentane through hexadecane are liquids; the homologues larger than hexadecane are solids. The boiling points of alkanes increase with molecular weight. Branching reduces the boiling point, the more branching the lower the boiling point. Alkanes are almost completely insoluble in water.

    23. Preparation of alkanes 1- Hydrogenation of unsaturated hydrocarbon: 2- Reduction of alkyl halides a- Hydrolysis of Grignard reagent

    24. b- Reduction by metal and acid c- From coupling with metal d- Using cuprate method

    25. Reaction of alkanes 1- Halogenation if we have one type of carbone If we have different type of carbone

    26. 2- combustion of alkanes 160 kcal\mol for each methylene group

    27. Cycloalkanes :       have one or more rings of carbon atoms

    28. Naming Cycloalkane Count the number of carbon atoms in the ring and the number in the largest substituent chain. If the number of carbon atoms in the ring is equal to or greater than the number in the substituent, the compound is named as an alkyl-substituted cycloalkane For an alkyl- or halo-substituted cycloalkane, start at a point of attachment as C1 and number the substituents on the ring so that the second substituent has as low a number as possible. Number the substituents and write the name

    30. Cis-Trans Isomerism in Cycloalkanes Rotation about C-C bonds in cycloalkanes is limited by the ring structure There are two different 1,2-dimethylcyclopropane isomers, one with the two methyls on the same side (cis) of the ring and one with the methyls on opposite sides (trans)

    31. Reaction of cycloalkanes Ring less stable Ring more stable 5 and 6

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