CHEM 2211 1st Edition Lecture 15 Outline of Last Lecture I II III Protons bonded to Oxygen and Nitrogen Deuterium in HNMR CNMR Spectroscopy Outline of Current Lecture I II Alkenes have double bonds Nomenclature Current Lecture I Alkenes have double bonds A The general formula for an alkene is CnH2n B Alkenes have two less carbons than alkanes C5H12 II C5H10 C Degree of unsaturation refers to the number of pi bonds present D Alkanes are considered saturated because they have the maximum number of bonds E The presence of pi bonds means the carbon is unsaturated Nomenclature A Replace the ane at the end of an alkane name with ene B Number the parent chain in an order that gives the functional group the lowest number double bond counts as a functional group 2 butene 1 butene i Use cis and trans for stereoisomers cis 2 pentene trans 2 pentene C For molecules with two double bonds replace ene with diene 1 4 pentadiene D Substituents are stated before the parent chain name The functional group on the parent chain always gets the lowest number 4 pentoxy 1 butene 4 methyl 1 3 pentadiene E Multiple substituents are stated in alphabetical order for further review refer to Section 3 2 in the book 5 bromo 4 chloro 1 heptane F If same number is found for two substituents when numbered both ways then the way with the lowest substituent number wins 2 bromo 4 methyl 3 hexene NOT 5 bromo 3 methyl 3 hexene G Double bonds in a ring are always labeled as carbons one and two then count ot give the substituents the lowest number 3 ethylcyclopentene H If the same number is found for alkene functional groups and for one or more substituents ignore the conflicting substituents and number in a way that gives the remaining substituent the lowest number 6 bromo 3 chloro 4 methylcyclohexene NOT 3 bromo 6 chloro 3 methylcycohexene i Sp2 carbons are called vinyl carbons and their adjacent carbons are called allylic carbons Vinyl Carbons Allylic Carbons I Using the E and Z method i Similar to cis and trans nomenclature ii E Z nomenclature refers to the orientation of the highest priority substituents when the substituents are not the same iii E means that the substituents are on the same side iv Z means the substituents are on the opposite side v Priority is based on the atomic number Z 1 bromo 2 chloropropene E 1 bromo 2 chloropropene
View Full Document