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Chapter 20: Organic Chemistry

Chapter 20: Organic Chemistry. The chemistry of carbon compounds. Mainly carbon and hydrogen atoms. Many organic compounds occur naturally. Thousands more can be synthesized by man. NaCl versus Butane. NaCl , 58.5 g/ mol Bonding is ionic M.P. = 801 o C B.P. = 1413 o C

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Chapter 20: Organic Chemistry

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  1. Chapter 20: Organic Chemistry • The chemistry of carbon compounds. • Mainly carbon and hydrogen atoms. • Many organic compounds occur naturally. • Thousands more can be synthesized by man.

  2. NaClversus Butane • NaCl, 58.5 g/mol • Bonding is ionic • M.P. = 801oC • B.P. = 1413oC • Dissolves in water • Will not burn • C4H10, 58.1 g/mol • Bonding is covalent • M.P. = -138oC • B.P. = 0oC • Not soluble in water • Will burn in air

  3. Molecular Geometry • There are three hybridization states and geometries found in organic compounds: • sp3Tetrahedral • sp2Trigonal planar • sp Linear

  4. Classes of Organic Compounds Aliphatic Aromatic Saturated Unsaturated Benzene Ring Alkanes Cycloalkanes Alkenes Alkynes

  5. Alkanes • “Saturated” hydrocarbons • All C-C single (sigma) bonds • Formula = CnH2n+2

  6. Formulas • Structure is very important in organic chemistry. • Propane = C3H8, chemical formula • Complete structural drawing – shows every single bond. H HH    H – C – C – C – H  H HH

  7. Formulas • Condensed structural drawing collapses the H atoms that are bonded to EACH carbon atom. • CH3 – CH2 – CH3 , condensed formula. • This is how a formula is written.

  8. Formulas • The molecule is really NOT linear, though. • The sigma bonds in the alkanes have free rotation.

  9. First Ten Alkanes: Base Names

  10. Structural Isomers • For four carbons, there are two ways to arrange. • For five carbons, there are three ways to arrange.

  11. IUPAC Nomenclature • A name of a compound consists of three parts. • Prefix, Base, and Suffix prefix base suffix substituents family longest chain (how many C’s)

  12. IUPAC Nomenclature • A substituent is any group that is attached to the longest chain of carbon atoms. • CH4 = methane, -CH3 = methyl • CH3CH3 = ethane, -CH2CH3 = ethyl • Cl = chloro, Br = bromo, I = iodo

  13. IUPAC Nomenclature • Find the longest chain in the molecule. • Number the chain from the end nearest the first substituent encountered. • List the substituents as a prefix along with the number(s) of the carbon(s) to which they are attached. • LEP #1

  14. Cycloalkanes • A ring structure can be constructed from alkanes of three or more carbons by removing two hydrogen atoms. • Because they form a geometric shape, a shorthand method for their structure is that shape. • Rings with 5 and 6 carbons are the most stable.

  15. IUPAC Nomenclature • For ring structures, a mono-substituted ring does not need a number. • Why??? • For di-substituted ring structures, number starting from the location of one the substituents and then go CW or CCW to give the next one the lowest number.

  16. Haloalkanes • A haloalkane is placing a halogen (group 7A) atom in place of a hydrogen atom. • Naming uses the fluoro, chloro, bromo, and iodo names. • Haloalkanes are used as refrigerants (CF3CH2F) and anesthetic agents (CF3CHClBr).

  17. Stereoisomerism and Optical Isomerism • Stereoisomers = molecules in which the atoms have the same connectivity, but have a different spatial arrangement. • Geometric = cis / trans (alkenes) • Optical isomers = are two molecules that are non-superimposable. • Optical isomers are much like your hands – they are not superimposable!

  18. Chirality • Any carbon with four unique groups bonded to it are said to be chiral.

  19. Chirality • If one of the two optical isomers is present, then it will rotate plane-polarized light to the left or to the right. • An equal amount of both isomers will not rotate the light and is said to be a racemic mixture.

  20. Chirality • Many important biochemical molecules are chiral. • Many important pharmaceuticals have at least one chiral carbon. • Ex) Ibuprofen Chiral Carbon

  21. Properties and Reactions of Alkanes • Alkanes are non-polar and, thus, do NOT dissolve in water. • Alkanes typically have a density of 0.65 – 0.70 g/mL and will float on the surface of water. • Alkanes are relatively unreactive. • They burn in air, though, to produce energy. • Halogenation: CH3CH3 + Cl2

  22. Alkenes • Called “unsaturated” • Contain at least one C=C double bond • Simplest alkene = C2H4

  23. Alkenes • The double bond does not allow for free-rotation.

  24. IUPAC Nomenclature • Naming an alkene. • Find the longest chain that includes the double bond. Suffix name uses –ene ending. • Number the chain so that the double bond gets the lowest numbers (has priority over other substituents). Only four carbons or longer will need a number for the double bond position. Use only the lowest number for start of double bond. • Number substituents based on this numbering. • Cycloalkenes – the double bond is ALWAYS position #1 and #2.

  25. Geometric Isomers • Some alkenes can have geometric isomers due to rigid shape around double bond. • Requires two different sets of groups on each side of the double bond – one large and one small. A B C = C B A • Opposite = trans, Same side = cis

  26. Addition Reactions • Alkenes undergo an “addition” reaction by adding a small molecule across the double bond. • Hydrogenation • Halogenation • Hydration

  27. Aromatic Hydrocarbons • Benzene, C6H6, is a ring structure like the cycloalkanes. • However, it is very different from the cycloalkanes, whose ring structures are fairly easy to break open. • Benzene is VERY stable and found in many important molecules like aspirin, vanillin, and acetaminophen. • What makes it unique?

  28. IUPAC Nomenclature • Mono-substituted benzene needs no number. • Some have special (common) names. • Toluene, Phenol, and Aniline. • Di-substituted benzene rings are numbered like the cycloalkanes. • Substituted toluenes, phenols, and anilines have those groups as the first position.

  29. Functional Groups • Addition of atoms like O, N, and S add reactivity and polarity to the alkanes. • Can occur in many different ways. • Will need to know the nomenclature and reactions of some and be able to identify all. • The letter “R” is a generic designation for an alkyl group.

  30. Alcohols • Alcohols contain the hydroxyl (OH) group. • R-OH • Alcohols are classified as primary, secondary, and tertiary. Primary (1º) Secondary (2º) Tertiary (3º)1 group 2 groups 3 groups H CH3CH3| | | CH3—C—OH CH3—C—OH CH3—C—OH| | | H H CH3

  31. IUPAC Nomenclature • Alcohols get an –ol suffix. • The –OH group MUST have the lowest number – it has priority. • On a cycloalkane, it is carbon #1. • On benzene it is called phenol.

  32. Properties of Alcohols • The –OH group can make the molecule soluble in water due to HB force. • C1 to C4 are very soluble in water. • More than five carbons, though, is virtually insoluble. • CH3 – CH2 – CH2 – CH2 – CH2 – CH2 - OH long chain is non-polar (dominates)

  33. Reactions of Alcohols • Oxidation = loss of two H’s or gain of O. • Depends on primary, secondary or tertiary. • Primary Alcohol  Aldehyde  Carboxylic Acid • Secondary Alcohol  Ketone • Tertiary  No Reaction

  34. Ethers • An O atom separating two alkyl groups. • R – O – R’ • Oxygen atom is polar, so smaller ones are soluble in water. • CH3 – CH2 – O – CH2 – CH3 • MTBE

  35. Thiols • A sulfur atom – usually with an H attached. • R – SH • CH3 – CH2 – SH, Ethanethiol • These compounds smell BAD! • One amino acid has this thiol group.

  36. Carbonyl Group • Many functional groups contain a C = O group. • Aldehyde = the C = O group is terminal. • R-CHO • CH3 – CH2 – C – H  O

  37. Carbonyl Group • Aldehydes use the –al suffix. • The carbonyl carbon is automatically the first position. • Ketone = the carbonyl group is in the middle of the chain. • Smallest ketone has three carbons

  38. Carbonyl Group • Ketones use an –one suffix. • Number is needed for five or more C’s. • Carboxylic Acid = carbonyl group with a hydroxyl group attached. • R – COOH • Are many of the weak acids seen in Ch. 16.

  39. Carbonyl Group • Formulas are written differently! • Ex) Acetic Acid

  40. Carbonyl Group • Naming acids – use the –oic suffix plus the name acid. • Like aldehydes, the –COOH group is terminal, so it is C #1. • Esters = has both the carbonyl and the ether type O atom. • R – COO – R’

  41. Carbonyl Group • An ester is made by the reaction of an alcohol and a carboxylic acid. • R – C – OH + HO – R’ R – C – O – R’   O O • The –OH and –H produce water.

  42. Amine • An amine contains the N atom. • These can be primary, secondary, or tertiary. • R –NH2 , R2 –NH , and R3 –N. • The N group has a lone pair that will accept a proton • Therefore, these are the weak bases from Ch. 16.

  43. Amide • Contain the carbonyl group AND the amine group. • R – (C=O) – NH2 • The N group can also have an R group. • Made by the reaction of a carboxylic acid plus an amine. • Similar to ester reaction.

  44. Polymers • A polymer is a long chain of repeating units called monomers. • Monomers are typically small alkenes. • Reaction is called an addition reaction and are referred to as addition polymers • Initiated by organic peroxide, R-O-O-R’, which is split into two fragments, 2 R-O Benzoyl peroxide

  45. Common Monomers • CH2=CH2, ethylene makes polyethylene. • Two forms – low density and high density • Uses: • CH2=CHCl, vinyl chloride makes PVC. • Uses: • CH2=CHCH3, propene makes polypropylene. • Uses: • CF2=CF2, tetrafluoroethene makes Teflon. • Uses:

  46. Common Monomers • CH2=CCl2, 1,1-dichloroethene makes Saran. • Uses: • CH2=CH(C6H5), phenylethene makes polystyrene. • Uses: • Recycling – uses a series of symbols and numbers to identify the type.

  47. Condensation Polymers • Polyurethanes, Nylons, Rayons, etc. are produced using the ester and/or amide reaction. • Monomer units have two functional groups per molecule. • PETE = ethylene glycol + terephthalic acid • Nylon 6,6 = adipic acid + hexamethylenediamine

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