CH 221 1st Edition Lecture 22 Outline of Last Lecture I. Alkynes’ Addition ReactionsII. π- ComplexIII. Internal AlkynesOutline of Current Lecture IV. Terminal and Internal AlkynesV. Lindlar CatalystsVI. Carbon-Carbon BondsVII. Reaction SubstitutionVIII. Inverted ConfigurationCurrent LectureIV. A terminal alkyne is less reactive than internal alkynes- Because of this, the rate of reaction will increase with a mercuric ion catalyst- Terminal alkynes form aldehydes- Internal alkynes form ketones- Addition of hydrogen forms an alkaneV. Lindlar Catalyst- Stops the process before am alkane is formed- The catalyst delivers the hydrogen to one side of the compound- The hydrogen attached to an sp carbon is the most acidic - Ex. HC (triple bond) CH has a pKa of 25- A strong base is necessary to remove hydrogen -−¿HO¿ is not strong enoughVI. Forming a new Carbon-Carbon bond requires two stepsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- All compounds in Group 2 have an electron withdrawing atom or group that is attached to an sp3 carbon- Substitution reaction- the electronegative group is replaced by another- Elimination reaction- electronegative group is eliminated along with a hydrogen- Alkyl halides have good “leaving” groups- R-F alkyl fluoride, R-Cl alkyl chloride, R-Br alkyl bromide, R-I alkyl iodineVII. Reaction Substitution- The atom replacing the halogen is a nucleophile- Rate α [alkyl halide][nucleophile] - Rate= k[alkyl halide][nucleophile] a SN2 reaction- K being the rate constant- Relative reactivities:- Most reactive methyl halide > 1º alkyl halide > 2º alkyl halide > 3º alkyl halide too unreactive to undergo SN2 reactionVIII. Inverted configuration- If the halogen is bonded to an asymmetric center the product will have the inverted configuration- Rate of reaction is dependent on the concentration of alkyl halide and nucleophile- Carbon undergoes a backside attack by the nucleophile- C-Br bond breaks as C-O bond forms- Methyl halides react the fastest and tertiary the slowest because of steric hindrance- Two primary alkyl halides can react at different rates- The configuration of the product is inverted relative to the configuration of the
View Full Document
Unlocking...