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ORGANIC CHEMISTRY BASICS OVERVIEW o ORGANIC CHEMISTRY Used to be considered chemistry of living things (or things that were once living… like petroleum) o 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 o Examples: petroleum, medicines, plastics, plants and animals…... (including YOU!!) o More than 90% of all known compounds contain Carbon (although it accounts for only 0.2% of the earth’s crust composition) o Over 6,000,000 organic compounds have been identified – and that number is increasing daily with the synthesis of new compounds in labs H H O H C C C H H H H H H H C C C H O H H C C H H H O H H C C C C C C H H H BENZENE CH3 O2N H NO2 H 2 - PROPANOL NO2 2,4,6 - TRINITROTOULENE O H2N H ETHANOL ACETONE H H C CH2CH2N(CH2CH3)2 PROCAINE H H H H H C C C C H H H H BUTANE H WHAT IS THE DEAL WITH PETROLEUM AND HOW DOES IT FIT INTO THE ORGANIC CHEMISTY SCHEME? o PETROLEUM … BLACK GOLD … TEXAS TEA o Petroleum is a NON-RENEWABLE organic resource o Consists of a mixture of HYDROCARBONS of many different carbon chain lengths o HYDROCARBONS : simplest organic compounds containing only C and H atoms with “Carbon backbones” that are inherent to organic compounds H H H H C C C H H H H H H H H C C C C H H H H H BUTANE PROPANE H H H C H H METHANE H H H H H H H H H C C C C C C C C H H H H H H H H H OCTANE HOW DO YOU KNOW HOW C’s and H’s WILL GET TOGETHER TO FORM HYDROCARBONS? o 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!) o We write LEWIS DOT STRUCTURES to show the sharing of electrons, and thus formation of bonds between atoms in Covalent compounds o First get the number of outer shell electrons from the Group # on Periodic table o 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 o 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 o 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 o Carbon needs to make 4 bonds o Oxygen needs to make 2 bonds o Hydrogen needs to make 1 bond o Nitrogen needs to make 3 bonds o Example of Lewis Dot structure for C and for H H C o 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 H H C H H H C H H H o Can also write MOLECULAR FORMULAS that do not show the individual bonds o Expanded Molecular Formula still shows how atoms are arranged: 2, propanol = CH3CH(OH)CH3 o 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: Oxygen Silicon Carbon Nitrogen Sulfur Phosphorus 2. Given the Expanded molecular formulas, first create a 3-D molecular model of the alkanes below. Then draw the correct STRUCTURAL FORMULAS. CH3CH2CH3 CH3CH3 CH3OH CH3CH2CH2CHCH3CH3 3. Use 3-D molecular models to create a reasonable structure from the condensed molecular formulas below. Draw a STRUCTURAL FORMULA once you are satisfied that your models are reasonable, taking into account how many bonds each element makes. C4H10 C6H14 4. Compare the structural formulas you drew for the molecules in Question 3 with another lab group. Did everyone come up with the same structure? If not, who is correct? 5. Try to arrange the atoms in the molecule C7H14 in different ways, while still keeping all of the atoms happy. Draw as many DIFFERENT structural formulas as you can below. CLASSES OF ORGANIC COMPOUNDS o HYDROCARBONS o ALKANES – simplest hydrocarbons – just C and H, and all single bonded – no funny business!! Propane = H H H H C C C H H H H o ALKENES – just like alkanes, but they have at least 1 carbon – carbon DOUBLE BOND Propene = H H H H C C C H H o 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 = H H C C C H H o NAMING HYDROCARBON CHAINS o Use IUPAC (International Union of Pure and Applied Chemistry) prefixes to tell number of carbons in longest chain o Add ending to tell the type of hydrocarbon (ane, ene, or yne) Number of Carbon atoms 1 2 3 4 5 6 7 8 9 10 Prefix Meth Eth Prop But Pent Hex Hept Oct Non Dec Structural Formulas and Naming of Alkanes and Isomers Lab Name ____________________ Date_________ Period_______ OBJECTIVE: To be able to assemble models of several simple hydrocarbons and relate the 3-D shapes of molecules to their names and structural formulas used to represent them on paper. PART 1 – STRAIGHT CHAIN ALKANES PROCEDURE: 1. Assemble a 3-D molecular model of methane (CH4) and draw the corresponding structural formula in Chart 1 on back of paper. 2. Repeat this process by adding one more C atom in place of a H in the methane molecule and adding enough H atoms to complete the 2 carbon molecule. Repeat this for the compounds with 3 – 10 Carbon atoms, keeping in mind the number of bonds that C and H need. 3. When you have successfully created and written structures for all of the alkanes listed in the chart, go back and find the correct prefix for the number of carbons and list them in the chart. 4. Now go back and correctly name each of the alkanes. 5. Finally, provide the condensed molecular formula for each alkane in the space provided in the chart. PART 2 – BRANCHED CHAIN ALKANES - A.K.A. ISOMERS 1. Assemble a 3-D molecular model with the molecular formula C4H10. 2. Create as many different arrangements of the atoms in C4H10 as you possible can, and draw the structural formulas below. 3. Check with your teacher to determine if you have the identified the correct number of ISOMERS – compounds with the same molecular formula, but different structural formulas (ways that the atoms are put together) 4. Now try to make as many different isomers of hexane (C6H14) as possible and draw the structural formulas below. CHART 1 Number of Carbon atoms 1 2 3 4 5 6 7 8 9 10 Prefix Name of Alkane Molecular formula (condensed) Structural formula QUESTIONS 1. What is the trend in the ratio of C to H in the molecular formulas from Chart 1? 2. Write the molecular formula for an alkane containing 25 Carbon atoms. 3. Did you decide to write the condensed or expanded molecular formula for the previous question? Why? 4. As the number of carbons in a chain increases, what seems to happen to the number of ISOMERS that can be made for the same molecular formula? 5. Would you expect all of the different ISOMERS of a compound like hexane to have the same physical and chemical properties? EFFECTS OF CARBON CHAIN LENGTHS HOW DO WE GET ALL OF THESE DIFFERENT PRODUCTS FROM THAT THICK BLACK SLUDGE? o 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 DIFFERENT CARBON CHAIN LENGTH FRACTIONS USED FOR? ASSIGNMENT: You Decide pg. 173 – Uses of Fractions HOW IS THE LENGTH OF THE CARBON BACKBONE CHAIN RELATED TO BOILING POINT? o INTERMOLECULAR FORCES are attractions between molecules of a particular substance (how much molecules of methane “like” each other for example) o Can be determined by the normal physical state of the substance (solid, liquid, gas) Number of Carbon atoms 1 2 3 4 5 6 7 8 9 10 Prefix Molecular formula Name of Alkane Melting Point (C) Boiling Point (C) Meth Eth Prop But Pent Hex Hept Oct Non Dec CH4 C2H6 C3H8 C4H10 C5H12 C6H14 C7H16 C8H18 C9H20 C10H22 methane ethane propane butane pentane hexane heptane octane nonane decane -182 -172 -187.7 -138.4 -129.7 -95 -90.6 -56.8 -51 -29.7 -161 -88 -42.1 -0.5 36.1 69 98.4 125.7 150.8 174.1 ASSIGNMENT: Your Turn pg. 132 – Alkane Boiling Point Trends ASSIGNMENT: Your Turn pg. 184 – Alkane Boiling Points: Isomers