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Intro to organic chemistry ( orgo )

Intro to organic chemistry ( orgo ). SCH4U – Unit B. Organic Compounds. Organic chemistry: chemistry of carbon compounds Exceptions are oxides of carbon (CO 2 and CO), carbonates, bicarbonates, and cyanides Carbon atoms are generally bonded to: Each other Hydrogen atoms

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Intro to organic chemistry ( orgo )

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  1. Intro to organic chemistry (orgo) SCH4U – Unit B

  2. Organic Compounds • Organic chemistry: chemistry of carbon compounds • Exceptions are oxides of carbon (CO2 and CO), carbonates, bicarbonates, and cyanides • Carbon atoms are generally bonded to: • Each other • Hydrogen atoms • Other specific elements (O, N, S, P and others)

  3. Why study organic chemistry? • Life is carbon-based. Everyone is made up of organic compounds. There are more known carbon compounds than any other element. • There are several million known organic compounds with ~30,000 more being “discovered” each year. • Some common organic compounds include plastics, synthetic and natural fibres, dyes, drugs, pesticides, lighter fluid, and gasoline.

  4. The carbon atom • Carbon has four valence electrons allowing it to form four bonds with other atoms by sharing its electrons • This results in a tetrahedral shape • Carbon forms covalent bonds (sharing of electrons) with carbon atoms

  5. Classification • Since organic compounds are composed almost entirely of carbon, they are sometimes referred to as hydrocarbons • Hydrocarbons can be divided into: • Aliphatics: carbon atoms in an open chain structure; may have branches, but no rings • Alicyclics: carbon atoms arranged in a ring structure • Aromatics: structures related to benzene (C6H6)

  6. Classification • Aliphatics can be further categorized into: • Alkanes: contains only single bonds (saturated) • Alkenes: contains at least one double bond (unsaturated) • Alkynes: contains at least on triple bond

  7. Isomers

  8. Isomers

  9. Isomers

  10. Diagrams & formulas • A number of different (but related) diagrams used to express structures in organic chemistry: • Empirical molecular formula • Expanded molecular formula • Complete structural formula • Condensed structural formula • Line structural formula • 3D structural formula

  11. Alkanes

  12. Alkanes • Only single bonds present in the main chain • General formula is CnH2n+2 • Form a tetrahedral shape • Note: more on shapes in the next unit • Create a 109.5° angle between bonds • Considered “saturated” because no other hydrogen atoms can be added • Always end in “~ane”

  13. Nomenclature • Three parts to organic chemistry nomenclature: • Prefix: indicates number, type and location of branches and/or functional groups (if any) • Root: indicates the number of carbon atoms in the main (parent) chain • Suffix: indicates the number and location of double or triple bonds (if any) and/or highest priority functional group

  14. Let’s draw alkanes! • Draw all ten basic alkanes and name them.

  15. Alkyl groups and branching • Each branch of a hydrocarbon is referred to as an alkyl group (if it contains only C and H) • Alkyl groups use the same basic roots as alkanes • Alkyls always end in “~yl” • Also contain a number and hyphen in front to indicate location on the main carbon chain • Example: 2-methyl pentane

  16. Alkyl groups and branching • Find the longest carbon chain and assign sequential numbers to each carbon • Assign these numbers temporarily starting from both ends of the carbon chain • Ultimately will select only one set of numbers to use • The goal is to use the numbering along the carbon chain that gives the lowest values assigned to branches

  17. Alkyl groups and branching • Let’s try some! Draw 3-ethyl octane…

  18. Alkyl groups and branching

  19. Alkyl groups and branching • When there is more than one branch, they are listed in front of the root and suffix according to alphabetical order of the name of the alkyl group • Try naming… • 4-ethyl 3-methyl heptane

  20. Alkyl groups and branching • If there is more than one of any given alkyl group • Indicate all the number for the positions using commas to separate the numbers, and • Use prefixes (on the prefixes – confused yet?) to indicate the number present

  21. Alkyl groups and branching • Try naming… • 5,6-diethyl-3,3,4-trimethyl nonane

  22. Alkenes • At least one double bond present in the main chain • General formula is CnH2n • Form a trigonal planar shape • Note: more on shapes in the next unit • Create a 120° angle between bonds • Considered “unsaturated” because other hydrogen atoms can be added • Always end in “~ene”

  23. Nomenclature • Identify and name the longest carbon chain that CONTAINS THE DOUBLE BOND(S). • Number the carbons in the chain so that the two carbons involved in the double bond have the lowest possible numbers. • If the double bond is equidistant from both ends, number the chain so that the substituent(s) have the lowest possibly number. • Follow same rules for identifying and naming prefixes.

  24. Nomenclature • Try naming this… • 2-ethyl 1-pentene

  25. Nomenclature • Now let’s draw 1-butene and 2-butene… 1-butene 2-butene

  26. Nomenclature • Let’s try a structure with more than one double bond… 1,3-pentadiene

  27. Nomenclature • Let’s put everything together and name… • 4-ethyl-3,6-dimethyl 1,2,4-octatriene

  28. Diastereomers • Consider the following compounds… cis-2-butene trans-2-butene 2-methyl- 1-propene

  29. Diastereomers • Not superimposable upon one another • Result from lack of free rotation around the double bond • Priorities are assigned to the two groups attached to the carbon atoms on either side of the double bond (starting with the carbon to the left of the double bond) based on atomic number • Largest atomic number at the first point of difference has the highest priority

  30. Diastereomers • If two highest priority groups are on the same side of the double bond (top or bottom)… • cis configuration • If two highest priority groups are on the opposite side of the double bond… • trans configuration

  31. Alkynes • At least one triple bond present in the main chain • General formula is CnH2n-2 • Form a linear shape • Note: more on shapes in the next unit • Create a 180° angle between bonds • Considered “unsaturated” because other hydrogen atoms can be added • Always end in “~yne”

  32. Nomenclature • Identify and name the longest carbon chain that CONTAINS THE TRIPLE BOND(S). • Number the carbons in the chain so that the two carbons involved in the triple bond have the lowest possible numbers. • If the triple bond is equidistant from both ends, number the chain so that the substituent(s) have the lowest possibly number. • Follow same rules for identifying and naming prefixes.

  33. Nomenclature • Try naming this… • 3,4-dimethyl 1-hexyne

  34. Nomenclature • Now let’s draw 1-butyne and 2-butyne… 1-butyne 2-butene

  35. Nomenclature • Let’s try a structure with more than one triple bond… 2,4-hexadiyne

  36. Nomenclature • Let’s put everything together and name… • 4-ethyl-4,5-dimethyl 2,6-octadiyne

  37. Alicyclics • Connected end-to-end forming a ring • Have single and/or double bonds present in the main chain • General formula is CnH2n • Can be “saturated” or “unsaturated” • Suffix changes depending on presence of double bonds • Prefix used is always “cyclo~” before the root

  38. Nomenclature • Try naming… cyclobutane cyclo-1-pentene cyclopent-1-ene

  39. Nomenclature • Try drawing… cyclo-1,4-hexadiene 2,7-diethyl-4-methyl cyclo-1,3,5-heptatriene

  40. Aromatics • Based on benzene and the presence of benzene-like rings • Benzene is a six-carbon ring with three double bonds • Cyclo-1,3,5-hexatriene • However, the electrons in the double bonds are actually spread over the whole molecule = delocalized • Benzene actually has six identical “1 ½” bonds

  41. Aromatics • Creates greater stability in the molecule • These “1 ½” bonds do not behave/react like double bonds • Molecules that have this type of sharing are referred to as aromatic compounds Benzene

  42. Aromatics • Some common aromatics… benzene napthalene antracene

  43. Nomenclature • Number carbons in benzene ring assigning lowest number to a branch. • If more than one branch exists, start numbering at the branch that contains the group with the highest priority (most complex). • Name branches attached to the benzene ring, assigning numbers to each branch. • If only one branch is present, a number does not need to be assigned. • Branches are placed before the root as a prefix.

  44. Nomenclature • Priority of branches on benzene…

  45. Nomenclature • When benzene has only two branches, position numbers do not have to be used • Instead, prefixes ortho-, meta-, and para- replace position numbers 1,2-dimethyl benzene ortho-dimethyl benzene

  46. Nomenclature 1,3-dimethyl benzene 1,4-dimethyl benzene meta-dimethyl benzene para-dimethyl benzene

  47. Nomenclature • IUPAC has retained many of the common names for aromatics…

  48. Nomenclature • Let’s try naming… 3-ethyl-5-methyl phenol

  49. Nomenclature • Let’s try drawing… 2,6-diethyl-3-methyl benzaldehyde

  50. Nomenclature • For use when: • Naming compounds with >1 fxn’l group • Naming compounds with a complicated substituent

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