alkynes Flashcards
general formula for alkynes
CnH2n-2
how many elements of saturation for each triple bond
2
physical properties of alkynes
nonpolar, insoluble in water
soluble in most organic solvents
boiling points are similar to alkanes of same size
less dense than water
up to four carbons; gas at room temp
bond angle of acetylene
180
is acetylide ion a strong nucleophile
yes
how do you synthesize alkynes
nucleophilic attack by the acetylide ion on an unhindered alkyl halide
what can acetylide ions also go through if the Sn2 reaction is not possible (hindered back side attack)
E2 reaction; can happen because acetylide ions are also strong bases
what forms when nucleophile attacks carbonyl group
alkoxide ion; when alkoxide is deprotonated, an alcohol forms
ketone
carbonyl group with two r groups
aldehyde
carbonyl group with one r group
formaldehyde
carbonyl group with no r group
what is ethchlorvynol used for
used to cause drowsiness and induce sleep
how is ethchlorovynol synthesized
addition of acetylide ion to carbonyl group
how does synthesis of alkynes by elimination reactions work
removal of twowh molecules from HX from a vicinal or geminal dihalide
when does triple bond migration occur
super basic conditions
characteristics of pi addition reactions
pi bond becomes two sigma bonds
exothermic
one or two more molecules may add
syn or anti addition, cis or trans double bond, or single bond`
catalytic hydrogenation
metal catalyst like pd, pt or ni is used, 2 hydrogen added to form alkane
lindlar’s catalyst
allows the reaction to stop after the addition of one mole of H; produces cis alkene
dissolving metal reduction
form trans alkene; anti stereochemistry; look for metal ammonia
keto - enol tautomerization
carbon oxygen double bond is more stable than carbon carbon double bond; rearranges so that the carbon carbon doubel bond is replaced with the carbon oxygen double bond
