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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
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
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
molecular geometry
Molecular Geometry
  • There are three hybridization states and geometries found in organic compounds:
    • sp3Tetrahedral
    • sp2Trigonal planar
    • sp Linear
classes of organic compounds
Classes of Organic Compounds

Aliphatic

Aromatic

Saturated

Unsaturated

Benzene Ring

Alkanes

Cycloalkanes

Alkenes

Alkynes

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

formulas1
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.
formulas2
Formulas
  • The molecule is really NOT linear, though.
  • The sigma bonds in the alkanes have free rotation.
structural isomers
Structural Isomers
  • For four carbons, there are two ways to arrange.
  • For five carbons, there are three ways to arrange.
iupac nomenclature
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)

iupac nomenclature1
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
iupac nomenclature2
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
cycloalkanes
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.
iupac nomenclature3
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.
haloalkanes
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).
stereoisomerism and optical isomerism
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!
chirality
Chirality
  • Any carbon with four unique groups bonded to it are said to be chiral.
chirality1
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.
chirality2
Chirality
  • Many important biochemical molecules are chiral.
  • Many important pharmaceuticals have at least one chiral carbon.
  • Ex) Ibuprofen

Chiral Carbon

properties and reactions of alkanes
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
alkenes
Alkenes
  • Called “unsaturated”
  • Contain at least one C=C double bond
  • Simplest alkene = C2H4
alkenes1
Alkenes
  • The double bond does not allow for free-rotation.
iupac nomenclature4
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.
geometric isomers
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
addition reactions
Addition Reactions
  • Alkenes undergo an “addition” reaction by adding a small molecule across the double bond.
    • Hydrogenation
    • Halogenation
    • Hydration
aromatic hydrocarbons
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?
iupac nomenclature5
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.
functional groups
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.
alcohols
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

iupac nomenclature6
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.
properties of alcohols
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)

reactions of alcohols
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
ethers
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
thiols
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.
carbonyl group
Carbonyl Group
  • Many functional groups contain a C = O group.
  • Aldehyde = the C = O group is terminal.
  • R-CHO
  • CH3 – CH2 – C – H



O

carbonyl group1
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
carbonyl group2
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.
carbonyl group3
Carbonyl Group
  • Formulas are written differently!
  • Ex) Acetic Acid
carbonyl group4
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’
carbonyl group5
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.
amine
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.
amide
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.
polymers
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

common monomers
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:
common monomers1
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.
condensation polymers
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