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Chemistry 102 Deming

Chemistry 102 Deming. Week 1 Wednesday 8-6-12. Chapter 11. Alkanes and Cycloalkanes. This prefix helps us talk about generalities without mentioning every specific one Example: the ending –ane means that the main chain has no double or triple bonds in it.

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Chemistry 102 Deming

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  1. Chemistry 102Deming Week 1 Wednesday 8-6-12

  2. Chapter 11 Alkanes and Cycloalkanes

  3. This prefix helps us talk about generalities without mentioning every specific one Example: the ending –ane means that the main chain has no double or triple bonds in it. An alkane is one (not specific which one) Alkanes are many (of those compounds that do not have double or triple bonds). This way we can say “all alkanes burn” without having to mention the over 150,000 unique ones. “Alk” a really useful prefix Alk: has carbon or strings of carbons

  4. Hydrocarbons • Hydrocarbon: a compound composed of only carbon and hydrogen. (maybe Cl, Br, I) • No O or N

  5. Ch 13 Ch 12 Ch 13 Fig. 11-7, p.351

  6. Alkanes • Alkanes: hydrocarbons containing only carbon-carbon single bonds. • The first two alkanes are methane and ethane.

  7. Alkanes • line-angle formula: • A line represents a carbon-carbon bond and a vertex and a line terminus represent a carbon atom. • Hydrogen atoms are not shown in line-angle formulas. Fullstructuralformula

  8. Root Name meth- (form-) eth- prop- but- pent- (amyl-) hex- hept- oct- non- dec- # of Carbons 1 2 3 4 5 6 7 8 9 10 Number of each side group

  9. Table 11-4, p.356

  10. 0 • Called Side groups Or Substituents Table 11-5, p.357

  11. Table 11-6, p.358

  12. Alkanes • Table 11.1 The first 10 alkanes with unbranched chains Did you notice that all of these hydrocarbons with just single bonds has the formula: CnH2n+2 • Remember that there are two levels of condensing: • Condensing the H’s • Condensing repeating groups

  13. Isomers • Isomers have the same molecular formula but are unique in how they are connected • Isomers come in two main typesStructural Isomers and Stereoisomers

  14. (different but have the same chemical formula) Isomers Stereo Isomers(come in pairs)(same name and numbering yet are still different from each other) Structural Isomers(unique name and numbering) Geometric Isomers Enantiomers • Also called cis-trans isomers • Found in rings and double bonds (have a top and bottom side) • Need two unique groups on two different atoms • Add cis- (same side) or trans- (across) in front of name • First discussed in Ch 11(rings) and Ch 12 (double bonds) • also called Optical Isomers • First discussed in chapter 17 (sugars) • Are molecules that are non-superimposable mirror images of each other • One kind is where there are four unique groups on a single carbon (chiral enantiomers) • Add + or – in front of name (or d, l or D, L or S, R)

  15. Structural Isomers(also called Constitutional isomers) Are made by moving atoms to another atom in the molecule to make it different Have unique name and/or numbering Be careful : If may look different because of the way you drew it. But if the model can be twisted, rotated and/or flipped and it then matches another one, it is not an isomer.

  16. Constitutional Isomerism • Constitutional isomers:compounds that have the same molecular formula but different structural formulas (different connectivity). • For the molecular formulas CH4, C2H6, and C3H8, only one structural formula is possible; there are no constitutional isomers for these molecular formulas. • For the molecular formula C4H10, two constitutional isomers are possible.

  17. Stereoisomers (in pairs) Have the same formula and SAME Name and numbering but still are different. are made if moving an elements on the same atom makes it different Are found in two categories : Geometric Isomers are also called cis-trans Isomers and can be found in rings (Ch 12) and double bonds (Ch 13). and Enantiomers (Ch18) which are also called optical isomers or mirror image isomers and we will discuss them in the carbohydrate chapter.

  18. Stereoisomers (in pairs) • Same formula and SAME Name and numbering • can be broken into : Geometric Isomers and Enantiomersare made if moving an element on the same atom makes it different

  19. Molecular formula and number of structural isomers(increases geometrically)

  20. More complex alkanes can be straight chained (normal) or branched.

  21. Fig. 11-10, p.352

  22. Fig. 11-11, p.352

  23. 2-methyl propane • (Common name) Fig. 11-13, p.353

  24. Fig. 11-12, p.353

  25. Constitutional Isomerism • Problem: do the structural formulas in each set represent the same compound or constitutional (structural) isomers? • Notice I will be looking for the longest chain then circle it, then name attachments as side groups

  26. Constitutional Isomerism • Solution: (if the names are the same they are the same) (a) They represent the same compound. • Solution:(if same formula but the names are different they are different) (b) They represent constitutional isomers. hexane hexane • 2,4-dimethylpentane • 2,3-dimethylpentane

  27. Constitutional Isomerism • Problem: draw structural formulas for the five constitutional isomers of molecular formula C6H14 • Solution:

  28. Conformations of Alkanes There is free rotation around C-C bonds.

  29. Conformations - Alkanes • Conformation: any three-dimensional arrangement of atoms in a molecule that results by rotation about a single bond. • following are three conformations for a butane molecule.

  30. Fig. 11-15, p.354

  31. Which of the following pairs represent structural isomers, and which are simply the same compound? Which are normal alkanes and which are branched alkanes? Notice all are CnH2n+2 = C5H2(5)+2 = C5H12

  32. Organic Hybridization Chart

  33. Bonding Characteristics In carbon, the 2s and three 2p orbitals can mix to produce four new sp3 hybrid orbitals

  34. The four hybrid sp3 orbitals allow carbon to form four bonds. When carbon is joined to four substituents (i.e. CH4), the resultant configuration is tetrahedral in shape.

  35. Fig. 11-4, p.345

  36. Fig. 11-5, p.345

  37. IUPAC Names • The IUPAC name of an alkane with an unbranched chain of carbon atoms consists of two parts: • (1) a prefix: the number of carbon atoms in the chain. • (2) the suffix -ane: shows that the compound is a saturated hydrocarbon (has only single bonds and no double or triple bonds).

  38. How many of each side group Root Name meth- (form-) eth- prop- but- pent- (amyl-) hex- hept- oct- non- dec- # of Carbons 1 2 3 4 5 6 7 8 9 10 • Endings (side group) • Endings (longest chain) • -yl side group of carbons • -ane has single bonds between carbons • -ene has a double bond between carbons • -yne has a triple bond (between carbons

  39. History of roots • Form- (ML formicarium=ant hill), formic acid was originally found by distilling dead ants. The first person to describe the isolation of this substance (by the distillation of large numbers of dead ants) was the English naturalist John Ray, in 1671 • Meth- from first isolation of methyl alcohol (1834, the French chemists Jean-Baptiste Dumas and Eugene Peligot ) They also introduced the word methylene to organic chemistry, forming it from Greek methy = "wine" + hŷlē = wood (patch of trees). Its intended origin was "alcohol made from wood (substance)" • Eth Its name was made from the name of ether, which at first meant diethyl ether. Which has 2 carbons • Prop Propionic acid was first described in 1844 by Johann Gottlieb, who found it among the degradation products of sugar. Over the next few years, other chemists produced propionic acid in various other ways, none of them realizing they were producing the same substance. In 1847, the French chemist Jean-Baptiste Dumas established that all the acids were the same compound, which he called propionic acid, from the Greek words protos = "first" and pion = "fat", because it was the smallest H(CH2)nCOOH acid that exhibited the properties of the other fatty acids, such as producing an oily layer when salted out of water and having a soapy potassium salt. • But-Its name was made from Greek βουτυρος = butter first given butyric acid. • Amyl- In biochemistry, amyl means "pertaining to starch". Many moderately complex biological chemicals related to starch contain the root, for example:In organic chemistry, amyl is the old trivial name for the radical called pentyl under the IUPAC nomenclature: that is, -C5H11. This usage may derive from the presence of amyl alcohol in fusel oil, itself often fermented from starches.

  40. Naming Alkanes The IUPAC method consists of: • THAT CONTAINS ANY SPECIAL THINGS In this chapter 12-13 it will be • Halogens (F, Cl, Br, I) or the NO2 group • Double or Triple Bonds

  41. IUPAC Names • The name of an alkane with a branched chain of carbon atom consists of: • a parent name: the longest chain of carbon atoms • substituent names: the groups bonded to the parent chain (or side groups)

  42. IUPAC Names • Alkyl group: a substituent group (side group) derived from an alkane by removal of a hydrogen atom. • commonly represented by the symbol R-. • named by dropping the -ane from the name of the parent alkane and adding the suffix -yl.

  43. 0 Table 11-5, p.357

  44. The iso and sec- side groups end Iso: always branching at the end (like a snake tongue) sec- : always branching one carbon at first carbon (like a sword) tert- : always branching two carbons at first carbon (like a better sword) begin branched linear sec-alkyl(secondary alkyl) Normal alkyl isoalkyl begin end ?

  45. Table 11-6, p.358

  46. IUPAC Names 1. The name for an alkane with an unbranched chain of carbon atoms consists of a prefix showing the number of carbon atoms and the ending -ane. 2. For branched-chain alkanes, the longest chain of carbon atoms is the parent chain and its name is the root name. 3. Name and number each substituent on the parent chain; use a hyphen to connect the number to the name.

  47. IUPAC Names 4. If there is one substituent, number the parent chain from the end that gives the substituent the lower number.

  48. IUPAC Names 5. If the same substituent occurs more than once: • Number the parent chain from the end that gives the lower number to the substituent encountered first. • Indicate the number of times the substituent occurs by a prefix di-, tri-, tetra-, penta-, hexa-, and so on. • Use a comma to separate position numbers.

  49. IUPAC Names 6. If there are two or more different substituents: • list them in alphabetical order. • number the chain from the end that gives the lower number to the substituent encountered first. • If there are different substituents in equivalent positions on opposite ends of the parent chain, give the substituent of lower alphabetical order the lower number.

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