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4th yr alkanes
 

4th yr alkanes

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  • Index of Hydrogen Deficiency – number of pairs of H atoms that must be added to the molecular formula of a compound to make it saturated= 1 per double bond= 1 per ring= 2 per triple bond
  • Natural gas is usually a mixture of small alkanes with low boiling points (methane, ethane, and propane). Crude oil, on the other hand, contains alkanes of all sizes that are then separated through a process called “fractional distillation,” during which compounds are separated by their boiling points.
  • Natural gas is usually a mixture of small alkanes with low boiling points (methane, ethane, and propane). Crude oil, on the other hand, contains alkanes of all sizes that are then separated through a process called “fractional distillation,” during which compounds are separated by their boiling points.
  • Natural gas is usually a mixture of small alkanes with low boiling points (methane, ethane, and propane). Crude oil, on the other hand, contains alkanes of all sizes that are then separated through a process called “fractional distillation,” during which compounds are separated by their boiling points.
  • As you’ve probably guessed, not all alkanes have all of their carbon atoms lined up in a nice row. As a result, we’ve got to consider what happens when these nice rows have other nice rows that branch off of them.
  • As you’ve probably guessed, not all alkanes have all of their carbon atoms lined up in a nice row. As a result, we’ve got to consider what happens when these nice rows have other nice rows that branch off of them.
  • Though it’s not intuitively obvious at this point why we would want to do this, it turns out to beuseful later because it’s often related to chemical reactivity.
  • Though it’s not intuitively obvious at this point why we would want to do this, it turns out to beuseful later because it’s often related to chemical reactivity.
  • Though it’s not intuitively obvious at this point why we would want to do this, it turns out to beuseful later because it’s often related to chemical reactivity.
  • Because the longest unbroken carbon chain in this molecule contains sevencarbon atoms (shown in bold), this molecule is a derivative of heptane.
  • Because the longest unbroken carbon chain in this molecule contains sevencarbon atoms (shown in bold), this molecule is a derivative of heptane.
  • Because the second drawing has a lower-numbered carbon at the first branchingpoint (the methyl at the 3 position as opposed to the ethyl at the 4 position), thenumbering in the second molecule is correct.
  • Because the longest unbroken carbon chain in this molecule contains sevencarbon atoms (shown in bold), this molecule is a derivative of heptane.
  • In our case, we have the substituents “3‑methyl” and “4‑ethyl” and the parent alkaneis heptane. Putting it together, this molecule is named “4‑ethyl-3‑methylheptane”(with no space between the “3‑methyl” and heptane). All substituent names are separatedfrom each other with dashes.
  • Hopefully you can see that the longest chain has six carbon atoms. If we numberthe carbon atoms correctly, we will start from the end closest to where the substituentsbranch off (which results in their being at the 2- and 3‑positions). Because bothgroups contain one carbon, they are named the “2‑methyl” and “3‑methyl groups.”Now, you might think that this compound should be called 2‑methyl-3‑methylhexane,but you’d be wrong. Whenever we have more than one substituent that has the samenumber of carbon atoms, we can combine them by using di-, tri-, tetra-, and penta- toindicate how many of this group are present. Numbers indicating the positions of thesubstituent branches are separated by a comma. As a result, this molecule is properlynamed “2,3‑dimethylhexane.”2,3‑dimethylhexane
  • As you can see, if you number the carbon atoms in one direction, you have the substituents“3‑methyl” and “4‑ethyl,” while if you number it the other way, you get the“3‑ethyl” and “4‑methyl” substituents.
  • Natural gas is usually a mixture of small alkanes with low boiling points (methane, ethane, and propane). Crude oil, on the other hand, contains alkanes of all sizes that are then separated through a process called “fractional distillation,” during which compounds are separated by their boiling points.
  • Natural gas is usually a mixture of small alkanes with low boiling points (methane, ethane, and propane). Crude oil, on the other hand, contains alkanes of all sizes that are then separated through a process called “fractional distillation,” during which compounds are separated by their boiling points.

4th yr alkanes 4th yr alkanes Presentation Transcript

  • Organic Compounds Hydrocarbons Aliphatic Aromatic Hydrocarbon Derivatives Halogen Containing Oxygen Containing Nitrogen Containing Classification of Organic Compounds
  • Hydrocarbons Aliphatic Saturated Unsaturated Aromatic Benzenes Polycyclic Benzene Classification of Organic Compounds
  • Aliphatic Saturated Alkanes Unsaturated Alkenes Alkynes Classification of Organic Compounds
  • Alkanes • are compounds that contain only C-C and C-H bonds • generally come from fossil fuels, particularly natural gas and crude oil • Formula is always CnH2n+2
  • Structural Formulas Alkanes are written with structural formulas that are • expanded to show each bond (Lewis Structure). • condensed to show each carbon atom and hydrogen atoms attached to that carbon. Expanded (Lewis) Condensed H H C H CH4 , methane H 5
  • Expanded and Condensed Structures 6
  • Structural Formulas Condensed formulas are written for expanded structural formula by showing each carbon and the attached hydrogen atoms. Expanded Condensed H H H H │ │ │ │ H─C ─C ─C ─C ─ H CH3─CH2─CH2─CH3 │ │ │ │ H H H H 7
  • Alkane Nomenclature •the names of all organic compounds stem from the names of the alkanes
  • Alkane Nomenclature • Straight chain alkanes are alkanes in which all the carbon atoms line up in a row. • Called unbranched or normal
  • Alkane Nomenclature Unbranched/ Normal Alkanes # C Name #C Name 1 Methane 11 Undecane 2 Ethane 12 Dodecane 3 Propane 13 Tridecane 4 Butane 14 Tetradecane 5 Pentane 15 Pentadecane 6 Hexane 16 Hexadecane 7 Heptane 17 Heptadecane 8 Octane 18 Octadecane 9 Nonane 19 Nonadecane 10 Decane 20 Eicosane
  • Alkane Nomenclature Pentane Heptane Propane Butane •Condensed Structural Formula •Actually Zig-Zag Structures •All Carbons sp3 Hybridized
  • Alkane Nomenclature Name the smaller rows that branch off of the larger rows as if they were little independent alkanes of their own, better known as alkyl groups.
  • Alkane Nomenclature Hexane or n-hexane Alkyl group: Methyl
  • Alkyl Group Nomenclature Unbranched Alkyl Groups # C Name #C Name 1 Methyl 11 Undecyl 2 Ethyl 12 Dodecyl 3 Propyl 13 Tridecyl 4 Butyl 14 Tetradecyl 5 Pentyl 15 Pentadecyl 6 Hexyl 16 Hexadecyl 7 Heptyl 17 Heptadecyl 8 Octyl 18 Octadecyl 9 Nonyl 19 Nonadecyl 10 Decyl 20 Eicosyl
  • Alkane Nomenclature The carbons in an alkane are sometimes classified by how many other carbon atoms are stuck to them.
  • 16 Alkane Nomenclature • Classified by the connection site – a carbon at the end of a chain (primary alkyl group) – a carbon in the middle of a chain (secondary alkyl group)
  • 17 Alkane Nomenclature • Classified by the connection site – a carbon with three carbons attached to it (tertiary alkyl group) – a quaternary (4°) carbon atom has four other carbon atoms bonded to it.
  • Alkane Nomenclature
  • Alkane Nomenclature butyl group or n-butyl
  • Alkane Nomenclature sec-butyl group
  • Alkane Nomenclature tert-butyl group
  • Alkane Nomenclature To name alkanes, we use the system that’s approved by the International Union of Pure and Applied Chemistry (IUPAC) for just this purpose.
  • Alkane Nomenclature To name alkanes, we use the system that’s approved by the International Union of Pure and Applied Chemistry (IUPAC) for just this purpose.
  • Alkane Nomenclature: Rule 1 • The root name for an alkane is based on the longest unbroken chain of carbon atoms (called the “parent chain”). Derivative of heptane
  • Alkane Nomenclature: Rule 1a When there are two longest chains of equal length, use the chain with the greater number of substituents as the main chain.
  • CH3 CH3—CH—CH2 CH—CH—CH2CH3 CH3 CH—CH3 CH3
  • Which is correct? Correct, 7-Carbon chain w/ 4 substituents
  • Alkane Nomenclature: Rule 2 • Assign numbers to each of the carbon atoms in this chain, beginning with the side that’s nearest the first point of branching. Correct numbering
  • Alkane Nomenclature: Rule 3 • Identify the names of the substituent groups and number them according to their position on the chain. 4-ethyl 3-methyl
  • Alkane Nomenclature: Rule 4 • Write the names of the substituents alphabetically, followed by the name of the parent alkane. 4-ethyl-3-methylheptane
  • Another example! 2,3-dimethylhexane
  • More Problems! • Problem 1: Write the name of the compound here. • Problem 2: Draw the 2,3,4-trimethylheptane molecule.
  • More Problems! • Problem 3: Write the name of the compound.
  • More Problems! If the numbers turn out the same way numbering it in both directions, the correct way to number it is by putting the alphabetically first substituent at the position with the lowest number. Correct numbering
  • More Problems! • Problem 3: Write the name of the compound. 3-ethyl-4-methylhexane
  • CH3 CH3—CH—CH2 CH—CH—CH2CH3 CH CH—CH3 CH3
  • Which is correct? Correct, 7-Carbon chain w/ 4 substituents
  • CH3 CH3—CH—CH2 CH—CH—CH2CH3 CH3 CH—CH3 CH3 Derivative of heptane
  • 3-ethyl-2,4,5-trimethylheptane
  • More Problems • Give the structures: a. 4-isopropyloctane b. 5-tert-butyldecane.
  • 4-isopropyloctane
  • 5-tert-butyldecane
  • Haloalkanes • Haloalkanes can be named just like alkanes, with the halogen atom treated as a substituent. Halogen substituents are named fluoro-, chloro-, bromo-, and iodo-. • When more than one halogen is present in the parent chain, they must be named alphabetically.
  • Haloalkanes 2-bromobutane 1,2-difluoropropane
  • Complex Substituents • Complex alkyl groups are named by a systematic method using the longest alkyl chain as the base alkyl group. • The base alkyl group is numbered beginning with the carbon atom (the “head carbon”) bonded to the main chain.
  • Complex Substituents The substituents on the base alkyl group are listed with appropriate numbers, and parentheses are used to set off the name of the complex alkyl group. A (1-ethyl-2-methylpropyl) group A propyl group
  • Complex Substituents 3-ethyl-5-(1-ethyl-2-methylpropyl)nonane A propyl group
  • 5-(1,2,2-trimethylpropyl)nonane