Naming Hydrocarbons Tutorial (nomenclature)

Transcription

1 Naming ydrocarbons Tutorial (nomenclature)

2 Drawing structures: it s all good 2-butene This is called the skeletal structure 3 This is called the condensed structure 3 = Using brackets can also shorten some formulas: ( 2 ) 4 vs

3 Background: formulas for s Alkanes= n 2n+2, enes= n 2n, ynes= n 2n-2 Remember enes, then think of what would happen if bond was single or triple instead. Provides some useful information (e.g. for compositional analysis, or to check work) annot always tell hydrocarbon type based on numbers (e.g. propyne vs. propadiene) Q - how many hydrogens in each of these: 6 carbon alkane Alkene: 22? 3

4 Background: formulas for s Q - how many hydrogens in each of these: Answer: 6 carbon alkane 14 Alkene: (2x5-2 = 10-2)

5 Naming: common vs. IUPA ommon names used in the 1800 s are still used for some compounds today: O O Formic acid Acetylene O 3 Acetone The International Union of Pure and Applied hemistry (IUPA) was established in 1900s Frequent revisions to nomenclature Systematic method allows an infinite number of compounds to be named given a few rules

6 Basic names of hydrocarbons ydrocarbon names are based on: 1) class 2) # of, 3) side chain type and 4) position 1) name will end in -ane, -ene, or -yne 2) the number of carbons is given by a Prefix 1 meth- 2 eth- 3 prop- 4 but- 5 pent- 6 hex- 7 hept- 8 oct- 9 non- 10 dec- Actually, all end in a, but a is dropped when next to a vowel. E.g. a 6 alkene is hexene Q - What names would be given to these: 7, 9 alkane 2, 4 alkyne 1, 3 alkene

7 Basic names of hydrocarbons Q - What names would be given to these: Answers: 7, 9 alkane 2, 4 alkyne 1, 3 alkene -heptane, nonane -ethyne, butyne -does not exist, propene

8 Mnemonic for first four prefixes First four prefixes Meth- Monkeys Eth- Eat Prop- Peeled But- Bananas

9 Other prefixes Pent- Oct- Dec- ex-, ept-, Non-

10 Numbering carbons in alkenes and alkynes Draw pentene 3 Q- ow do we know where the double bond is? A-We number atoms (number carbons so that the multiple bond has the lowest number) pentene pentene

11 Numbering carbons Name these: 3 3

12 Numbering carbons Answers: 3 2-butene 3 3-nonyne

13 yclic structures yclic structures are circular ave cyclo in name cyclopentane Q- Draw these: cyclobutene cyclopropane

14 yclic structures Q- Draw these: cyclobutene cyclopropane

15 Naming side chains Names are made up of: side chains, root 2,3-dimethylpentane Root is the longest possible chain Must contain multiple bonds if present Add -yl to get name of side chain ommon side chains include: - methyl 2 - ethyl 2 3 * propyl ( ) 2 - isopropyl iso (branched) is not an IUPA convention Br- (bromo), l- (chloro), F- (fluoro), I- (iodo)

16 Naming side chains Example: use the rules on the bottom of the slide to name the following structure Rule 1: choose the correct ending ene

17 Naming side chains Rule 2: Find the longest carbon chain (note: since this is an alkene, we choose the longest carbon chain that includes the double bond) ene

18 Naming side chains Rule 3: attach prefix (according to # of ) 1-hexeneene

19 Naming side chains Rule 4: Assign numbers to each carbon You try numbering the carbons now.

20 Naming side chains Rule 4: Assign numbers to each carbon (note: chain is number to give double bond the lowest number) 1-hexene

21 Naming side chains ethyl methyl methyl Rule 5: Determine name for side chains 1-hexene

22 Naming side chains ethyl methyl methyl Rule 6: When more than one of the same side chains are present, use carbon numbers and the di, tri, tetra prefixes before the side chain name: 4,4-dimethyl

23 Naming side chains ethyl methyl methyl Rule 6: Attach name of branches in alphabetical order: 2-ethyl-4,4-dimethyl-1-hexene Note: we alphabetize the side chain names, do not alphabetize based on the di, tri, etc. prefixes

24 Practice: Naming side chains Name the following compounds:

25 Answers: methylhexane 4-ethyl-2,3-dimethylheptane ethyl-2,4,6-trimethyloctane

26 Naming side chains Name the structure below:

27 Answer: Naming side chains ethyl-2-methylpentane

28 Aromatic Nomenclature There are 2 naming methods 1) Numbering carbons 2) ortho, meta, para (stomp) ST Ortho Meta 3 3 1,2-dimethylbenzene orthodimethylbenzene 3 3 Para 1,3-dimethylbenzene metadimethylbenzene Benzene is very stable (does not generally undergo addition) 3 1,4-dimethylbenzene paradimethylbenzene