University:
York University
Course:
CHEM 1000 | Chemical Structure
Academic year:

2021
Views:

357

Pages:

3
Author:

Niklas

Lecture 5 (01/26/21) * Alkanes & Cycloalkanes 1. General Formula = CnH2n+2 where n≥0 (non-cyclic) → Fully Saturated 2. Non-polar molecules → No large dipoles (C=2.55 H=2.20) 3. IF LD FORCES → As molecules get larger - there is a greater As for Overlap higher IF 4. Strong Bonds: C-C (90 kcal/mol) C-H (101 kcal/mol) → Alkanes are generally unreactive in most cases - cont. Strong NP Bonds → used for their physical properties → E stored in alkanes can be used as a fuel source Nomenclature: IUPAC - systematic, unambiguous TRIVIAL - limited, but important Example: CH4 Methane C2H6 Ethane C3H8 Propane C4H10 Butane C5H12 Pentane C6H14 Hexane C7H16 Heptane C8H18 Octane C9H20 Nonane C10H22 Decane C11H24 Undecane 2. ID Substituents Parent chain Subst: methyl 3. # Parent Chain (two choices) #C to which Substit. is attached # + name, Minimize #'s Example: 3-Methyl-4,5,6-triethylnonane 12-methylheptane Goal: Be able to look at structure & write name, or vice versa. Fenestrane C10H16 **Tips for Naming Alkanes:** 1. If there's a subst equally distant from ea. end of Parent chain, # the C starting @ the end that is closer to the 2nd subst. [Image of a carbon chain with numbered carbons] **That doesn't work - whichever comes first in the alphabet goes first** [Image of a carbon chain with numbered carbons] Ex: [Image of a carbon chain with substituents] *Alphabetical* 4-ethyl-2-methyl hexane * FOR BRANCHED SUBST.: * Entire Name of Branched Subst. are Placed in Parenthesis * & are treated like any other Subst. 3-ethyl (5-propyl-1-methyl) 9 8 7 6 5 4 3 2 1 NONANE * 3-ethyl-5-(1-methylpropyl) NONANE * Alphabetical * Branched Subst. in () Ex: 4 5 6 | | 3 2 1 4-(1-methylethyl) heptane * NOT Alphabetical * Need to est. location