ORGANIC CHEMISTRY BASICS

OVERVIEW

Organic ChemistryUsed to be considered chemistry of living things (or things that were once living… like petroleum)

Since it has been demonstrated that organic compounds can be synthesized in laboratories we now just say that Organic chemistry is the Chemistry of Carbon compounds

  • Examples: petroleum, medicines, plastics, plants and animals…... (including YOU!!)

More than 90% of all known compounds contain Carbon (although it accounts for only 0.2% of the earth’s crust composition)

Over 6,000,000 organic compounds have been identified – and thatnumber is increasing daily with the synthesis of new compounds in labs







Some Examples:


What is the Deal with petroleum and how does it fit into the organic chemisty scheme?

PETROLEUM … Black Gold … Texas Tea

  • Petroleum is a Non-renewable organic resource
  • Consists of a mixture of hydrocarbons of many different carbon chain lengths
  • Hydrocarbons : simplest organic compounds containing only C and H atoms with “Carbon backbones” that are inherent to organic compounds



Some examples:



  • Carbon bonds contain potential energy (actually all bonds contain energy) – the beauty of petroleum is that the long chains of carbons connected to one another contain a lot of bonds – and therefore a lot of potential energy
  • Petroleum is used for:

Gasoline

Heat / electricity

Raw materials for:

  • Plastics: Polyethylene, Vinyl, Polypropylene…
  • Pharmaceuticals: Lipitor, Prozac, Coumadin…
  • Synthetic fibers: Nylon, Rayon, Teflon, Kevlar…

A quote from our nutty Russian friend Mendeleev regarding using petroleum as an energy source: he said it would “be akin to firing up a kitchen stove with a bank note”

HOW DO WE GET ALL OF THESE DIFFERENT PRODUCTS FROM THAT THICK BLACK SLUDGE?

  • Petroleum removed from the ground as “Crude Oil” is sent to the Refinery for processing – separating by distillation into fractions of similar carbon chain lengths

WHAT ARE THE POLITICAL RAMIFICATIONS OF BEING A SOCIETY THAT IS SO DEPENDENT ON PETROLEUM AS AN ENERGY SOURCE?

60% of all the petroleum in the world is in 5 countries: Iran, Iraq, Kuwait, Saudi Aradia, and UAE

The U.S. petroleum reserves from Prudhoe Bay in Alaska would be enough to supply our energy needs for less than 2 years

Petroleum cost is determined by supply/ demand (or projected supply/demand) i.e. What happened the day after 9/11 at the gas pumps?

The search for alternative fuels in the 80’s ceased due to cheap crude oil prices (70-90 cent/gallon gas prices)… we got lazy

Gee Dubya just proposed a 2000$ tax write off for anyone who owns a hybrid gas – electric car (the irony here is that the electricity that is the alternative fuel for the car is most probably obtained from burning petroleum at the power plant!)

HOW DO YOU KNOW HOW C’s and H’s WILL GET TOGETHER TO FORM HYDROCARBONS?

The Octet Rule says that everybody (except H and He) wants to have 8 outer shell electrons, Carbon has only 4 (it’s glass is both half empty and half full) – so instead of giving or taking electrons (Ionic bonding) it SHARES electrons – A.K.A Covalent Bonding forms Molecular compounds – (organic stuff!)

We write Lewis Dot Structures to show the sharing of electrons, and thus formation of bonds between atoms in Covalent compounds

  • First get the number of outer shell electrons from the Group # on Periodic table
  • Arrange electrons (dots) so that there is one dot on each of 4 sides of elements symbol, only double them up as pairs when you have more than 4
  • On the sides of the symbol where there is only 1 electron you will need to create a bond with another element to have a shared pair of electrons

When Carbon shares electrons to fulfill it’s outer shell – it needs to share with other atoms to get 4 more electrons – so it needs to make 4 bonds

  • Carbon needs to make 4 bonds
  • Oxygen needs to make 2 bonds
  • Hydrogen needs to make 1 bond
  • Nitrogen needs to make 3 bonds



Example of Lewis Dot structure for C and for H



A shared pair of electrons between 2 atoms is a bond, and the 2 dots representing the bond can be replaced by a line connecting the atoms – this is called a Structural formula

Can also write MOLECULAR FORMULAS that do not show the individual bonds

  • Expanded Molecular Formula still shows how atoms are arranged:
  • 2, propanol = CH3CH(OH)CH3
  • Condensed Molecular Formula just shows the number of each atom:
  • 2, propanol = C3H8O

ASSIGNMENT: PRACTICE WRITING LEWIS DOT STRUCTURES, STRUCTURAL FORMULAS, AND MOLECULAR FORMULAS

  1. Draw Lewis Dot Structures for the following elements:

OxygenSiliconCarbon

NitrogenSulfurPhosphorus

  1. Given the Expanded molecular formulas, draw the correct structural formulas for the following organic compounds:

CH3CH2CH3CH3CH3

CH3OHCH3CH2CH2CHCH3CH3

  1. Write a feasable structural formula for the condensed molecular given below:

C4H10

Classes of ORGANIC COMPOUNDS

  • Alkanes – simplest hydrocarbons – just C and H, and all single bonded – no funny business!!

  • Propane =
  • Alkenes – just like alkanes, but they have at least 1 carbon – carbon double bond

  • Propene =
  • ALKYNES – you know what they say… “it takes all kines” tee hee – just like alkanes, but they have at least 1 Carbon – Carbon triple bond

  • Propyne =
NAMING HYDROCARBONS
Number of Carbon atoms / Prefix / Molecular formula / Name of Alkane / Structural formula
1 / Meth / CH4
2 / Eth / C2H6
3 / Prop / C3H8
4 / But / C4H10
5 / Pent / C5H12
6 / Hex / C6H14
7 / Hept / C7H16
8 / Oct / C8H18
9 / Non / C9H20
10 / Dec / C10H22
Number of Carbon atoms / Prefix / Structural formula / Molecular formula / Name of Alkane / Melting Point (C) / Boiling Point (C)
1 / Meth / CH4 / methane / -182 / -161
2 / Eth / C2H6 / ethane / -172 / -88
3 / Prop / C3H8 / propane / -187.7 / -42.1
4 / But / C4H10 / butane / -138.4 / -0.5
5 / Pent / C5H12 / pentane / -129.7 / 36.1
6 / Hex / C6H14 / hexane / -95 / 69
7 / Hept / C7H16 / heptane / -90.6 / 98.4
8 / Oct / C8H18 / octane / -56.8 / 125.7
9 / Non / C9H20 / nonane / -51 / 150.8
10 / Dec / C10H22 / decane / -29.7 / 174.1

Carbon chain lengths effect physical properties of the compounds – check out how the intermolecular forces between carbon compounds with increasing numbers of carbons effects the boiling points of these compounds – Your turn pg. 175)

You Decide pg. 173 – uses of fractions

UNIT III C – Petroleum as an Energy Source

C.2 – Energy

Q: Where does ALL of our energy come from originally?

Q: How many different types of energy can you thinkof?

Q: Can you draw a picture showing how the energy from the sun becomes energy in my muscles (I’m a carnivore by the way!!)

Photosynthesis – radiant energy from the sun converted to chemical energy in plants

Biomolecules – organic molecules in plants and animals

Q: What sources of energy did we use 100 years ago?

Q: What changed? What made this become insufficient?

C.3 – Energy and Fossil Fuels

  • “Fossil” fuels contain chemical potential energy
  • Chemical reaction of burning fossil fuels results in release of energy we can use
  • Determination of what is a “good” fuel depends on net result of the bond-breaking and bond-forming steps
  • Consider the burning of methane:
  • CH4 + 2 O2CO2 + 2H2O + energy
  • Bond breaking – Endothermic (requires energy input)
  • Energy + CH4 + 2O2C + 4H+ 4O
  • Bond forming – Exothermic (gives off energy)
  • C + 4H + 4OCO2 + 2 H2O + Energy
  • This overall reaction is exothermic,… so methane is a pretty good fuel!!
  • If a reaction is exothermic, then the reverse reaction will be endothermic
  • CH4 + 2 O2CO2 + 2H2O + energy
  • energy + CO2 + 2H2O CH4 + 2 O2
  • Can you see why it would not be advantageous to put the combustion products of petroleum back together to make “new” fuel??

Q: How do you get the energy to cook your Ramen noodles (start from the very beginning…)

Q: Is each conversion 100% efficient?

Q: would it surprise you to know that gas engines are only 25% efficient at energy conversion?

  • Law of conservation of Energy : total energy of the universe is constant – never created or destroyed

UNIT III D – Useful Organic Materials

D.1 & D.2– Beyond Alkanes

  • Alkanes – (CnH2n+2)
  • Simplest organic compounds
  • Made of only H’s and C’s with only single bonds
  • Saturated : bonded to the maximum number of atoms possible (4 for C)
  • Alkenes – (CnH2n)
  • hydrocarbons with only 3 atoms bonded to a carbon atom within the compound
  • Still fulfill the octet rule – but by sharing two sets of electrons between atoms – called a double covalent bond
  • Unsaturated – because they are not bonded to the maximum number of atoms possible (only 3 other atoms for alkenes)
  • Alkynes – (CnH2n-2)
  • hydrocarbons with only 2 atoms bonded to a carbon within the compound
  • Still fulfill the octet rule - but by sharing 3 sets of electrons between atoms – called a triple covalent bond
  • Cycloalkanes – carbon backbones form closed rings
  • Aromatic Compounds
  • Contain benzene rings (C6H6)
  • Used widely as starting materials in drugs and dyes

D.4 – More Complicated Organic Compounds

  • Can also add other elements such as O, N, S, Cl
  • Still “organic” because they contain mostly C’s and H’s
  • Functional groups – characteristic atom(s) that make an organic compound have certain properties
  • Alcohols
  • Carboxylic Acids
  • Esters
  • Amines

D.5 – Petrochemicals and Polymers