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Introduction to organic chemistry

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  1. Introduction to organic chemistry

  2. Organic compounds • “Organic” originally referred to any chemicals that came from Organisms • Organic chemistry is the study of the compounds of carbon • Carbon atoms are unique because they form strong covalent bonds with each other • Composition of organic compounds: C,H,N,O,halogens (Cl,Br)

  3. A. Carbon Bonding • When carbon has 4 atoms bound to it these atoms have a tetrahedral shape.

  4. Hydrocarbons Hydrogen + Carbon • An organic molecule (hydrocarbon) is formed when carbon bonds to hydrogen. The simplest hydrocarbon consists of 4 hydrogen atoms bonded to a carbon atom (called methane) In addition to binding to hydrogen, carbon can also bind to other carbon atoms, as illustrated below:

  5. In fact the uniqueness of carbon comes from the fact that it can bind to itself. Carbon atoms can form long chains: branched chains: rings

  6. in fact, there appears to be almost no limit to the number of different structures that carbon can form. To add to the complexity of organic chemistry, neighboring carbon atoms can form double and triple bonds in addition to single carbon-carbon bonds A carbon-carbon single bond A carbon-carbon double bond A carbon-carbon triple bond

  7. Saturated Hydrocarbons • Saturated hydrocarbons • Have the maximum number of hydrogen atoms attached to each carbon atom. • Are alkanes and cycloalkanes with single C-C bonds. • CH3—CH2—CH3

  8. Unsaturated Hydrocarbons • Unsaturated hydrocarbons • Have fewer hydrogen atoms attached to the carbon chain than alkanes. • Are alkenes with double bonds. • Are alkynes with triple bonds.

  9. Formulas • Molecular formulas just tell you what kinds of atoms are in the molecule, but they don’t tell you how they are attached • structural formulas show you the attachment pattern in the molecule • In expanded structural formulas, all the individual bonds are drawn. • In condensed structural formulas, each carbon is written with the H atoms connected to it. • models not only show you the attachment pattern, but give you an idea about the shape of the molecule

  10. Line-Angle Formulas • Each angle, and beginning and end represent a C atom • H omitted on C • included on functional groups • double line is double bond, triple line is triple bond • Multiple bonds indicated

  11. Formulas

  12. Formulas

  13. C1 – C5:Are Gasesat Room Temperature C15: Are Solids at Room Temperature C6 - C15: Are Liquids at Room Temperature

  14. Types of Carbon Atoms • Primary carbon (1o) • a carbon bonded to • one other carbon • Secondary carbon (2o) • a carbon bonded to • two other carbons • Tertiary carbon (3o) • a carbon bonded to • three other carbons

  15. Functional Groups • other organic compounds are hydrocarbons in which functional groups have been substituted for hydrogens • a functional group is a group of atoms that show a characteristic influence on the properties of the molecule • generally, the reactions that a compound will perform are determined by what functional groups it has • since the kind of hydrocarbon chain is irrelevant to the reactions, it may be indicated by the general symbol R CH3—OH R group functional group

  16. An alcohol contains the hydroxyl (-OH) functional group. In an ether, an oxygen atom is bonded to two carbon atoms. –C–O–C– . An aldehyde contains a carbonyl group (C=O), which is a carbon atom with a double bond to an oxygen atom. In a ketone, the carbon of the carbonyl group is attached to two other carbon atoms. Carboxylic acids contain the carboxyl group, which is a carbonyl group attached to a hydroxyl group. O ║ — C—OH An ester contains the carboxyl group between carbon atoms. In amines, the functional group is a nitrogen atom. | —N —

  17. Alkanes • paraffins • aliphatic • general formula CnH2n+2for chains • Straight-Chain Alkanes Combined with the -ane ending is a prefix for the number of carbons • very unreactive • come in chains or/and rings • CH3 groups at ends of chains, CH2 groups in the middle • chains may be straight or branched • saturated • branched or unbranched

  18. Naming Alkanes • The name for an alkane is based on Greek root with the suffix –ane.

  19. Alkanes – saturated hydrocarbons(CnH2n+2) methane ethane hexane 3-methylpenthane ! Alkanes are not planar !

  20. Alkyl Groups An alkyl group • is composed of one or more carbon atoms attached to a carbon chain • Is derived from the corresponding alkane by removing one hydrogen • Is named by replacing the –ane ending of the corresponding alkane with –yl • Derived from methane is methyl and from ethane is ethyl

  21. H C H - , M E T H Y L H C 3 H H H C H C H - , E T H Y L H C C 3 2 H H H H H C H C H C H - , P R O P Y L H C C C 3 2 2 H H H H C H 3 ( C H ) C H - , I S O P R O P Y L H C C 3 2 H H Alkyl Groups

  22. Naming • Each name consists of 3 parts • prefix • indicates position, number, and type of branches • indicates position, number, and type of each functional group • parent • indicates the length of the longest carbon chain or ring • suffix • indicates the type of hydrocarbon • ane, ene, yne • certain functional groups Prefix- Parent- Suffix where are the substituents How many carbons What family?

  23. Summary: IUPAC (International Union of Pure and Applied Chemistry) Rules for Alkane Nomenclature 1. Find and name the longest continuous carbon chain. This is called the parent chain. (Examples: methane, propane, etc.) 2. Number the chain consecutively, starting at the end nearest an attached group (substituent). 3. Identify and name groups attached to this chain. (Examples: methyl-, bromo-, etc.) 4. Designate the location of each substituent group with the number of the carbon parent chain on which the group is attached. Place a dash between numbers and letters. (Example: 3-chloropentane) 5. 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. Place a comma between multiple numbers. (Example: 2,3-dichloropropane)

  24. Example –Name the alkane • find the longest continuous C chain and use it to determine the base name since the longest chain has 5 C the base name is pentane

  25. Prefixes for # of Carbons

  26. Endings • Alkanes (all C-C single bonded parent chain) end in –ane • MethaneCH4 • EthaneC2H6 • PropaneC3H8 • Attached carbon groups (substituents) end in –yl • Methyl CH3 - • EthylCH3CH2- • PropylCH3CH2CH2 – 3-ethylpentane

  27. Step 2. Number the parent chain. • Number the parent chain so that the attached groups are on the lowest numbers Methyl is on carbon #2 of the parent chain Methyl is on carbon #4 of the parent chain 1 2 3 4 5 GREEN is the right way for this one! 5 4 3 2 1 • 2 • 3 7 8 • 4 5 6 8 7 6 2 1 5 4 3 • 2 3 4 5 6 • 7 • 6 5 4 3 2 • 1 Groups on 2 and 5 Groups on 4, 6, and 7 Groups on 2, 3, and 5 Groups on 3 and 6

  28. Step 3. Name the attached groups. • Carbon (alkyl) groups • Methyl CH3 - • EthylCH3CH2- • PropylCH3CH2CH2 – • Halogens • Fluoro (F-) • Chloro (Cl-) • Bromo (Br-) • Iodo (I-)

  29. Step 4. Designate where the group is attached to the parent chain. • Use the numbers of the parent chain from step 2 to designate the location of the attached groups to the parent chain. 2-methyl 1 2 3 4 5

  30. Step 5. Alphabetize the groups, combine like groups, and assemble. • The prefixes di, tri, tetra etc., used to designate several groups of the same kind • Prefixes are not considered when alphabetizing (Example: dimethyl = m for alphabetizing) • Parent chain goes LAST 1,1,1-trichloro-1-fluoromethane 1,1-dichloro-1,1-difluoromethane

  31. Practice – Name the Following 3-ethyl-2-methylpentane

  32. Practice – Name the Following CH3 CH2 CH CH3 CH CH3 CH3 2,3-dimethylpentane 5-ethyl-3,4-dimethyloctane

  33. Alkenes • also known as olefins • aliphatic, unsaturated • C=C double bonds • formula for one double bond = CnH2n • subtract 2 H from alkane for each double bond • trigonal shape around C • flat • much more reactive than alkanes • polyunsaturated = many double bonds

  34. Alkynes • also known as acetylenes • aliphatic, unsaturated • CºC triple bond • formula for one triple bond = CnH2n-2 • subtract 4 H from alkane for each triple bond • linear shape • more reactive than alkenes

  35. Naming Alkenes and Alkynes • change suffix on main name from -ane to -enefor base name of alkene, or to -yne for the base name of the alkyne • number chain from end closest to multiple bond • number in front of main name indicates first carbon of multiple bond

  36. Name the Alkene • find the longest, continuous C chain that contains the double bond and use it to determine the base name since the longest chain with the double bond has 6 C the base name is hexene

  37. Name the Alkene • identify the substituent branches there are 2 substituents one is a 1 C chain, called methyl the other one is a 2 C chain, called ethyl

  38. 3 4 4 3 2 1 5 6 Name the Alkene • number the chain from the end closest to the double bond then assign numbers to each substituent based on the number of the main chain C it’s attached to

  39. 3 4 4 3 2 1 5 6 Name the Alkene • write the name in the following order • substituent number of first alphabetical substituent –substituent name of first alphabetical substituent – • use prefixes to indicate multiple identical substituents • repeat for other substituents • number of first C in double bond –name of main chain 3–ethyl– 4–methyl– 2–hexene

  40. Practice – Name the Following

  41. Practice – Name the Following 3 4 5 6 2 1 3,4-dimethyl-3-hexene

  42. Name the Alkyne • find the longest, continuous C chain that contains the triple bond and use it to determine the base name since the longest chain with the triple bond has 7 C the base name is heptyne

  43. Name the Alkyne • identify the substituent branches there are 2 substituents one is a 1 C chain, called methyl the other one is called isopropyl

  44. 7 6 5 4 3 2 1 6 4 Name the Alkyne • number the chain from the end closest to the triple bond then assign numbers to each substituent based on the number of the main chain C it’s attached to

  45. 7 6 5 4 3 2 1 6 4 Name the Alkyne • write the name in the following order • substituent number of first alphabetical substituent –substituent name of first alphabetical substituent – • use prefixes to indicate multiple identical substituents • repeat for other substituents • number of first C in double bond –name of main chain 4–isopropyl– 6–methyl– 2–heptyne