Alkynes and cycloalkynes Flashcards
unsaturated hydrocarbons where some hydrogens have been replaced by triple carbon-carbon bonds
alkynes
General Formula of alkynes
CnH2n-2
Carbons in triple bond are __ __ and have __ geometry
- sp hybridized
- linear
sp hybridized angle
180
sp2 hybridized angle
120
sp3 hybridized angle
109.5
3 bonds of alkynes
- 1 sigma bond
- 2 pi bonds
carbon triple bond is __ than carbon double bond
stronger
bond length of triple bonds compared to double bonds
shorter
__ __ are easy to break. Opening opportunity for reactions
unsaturated hydrocarbons
open bonds from the uncoiling of triple and double bonds, the opened bonds could provide connections for carbon atoms to attach to
polymerization
How to name alkynes
- find longest chain with triple bond
- start counting closest to triple bond
- in presence of alcohol, number starting to closest alcohol
suffix of alkynes with alcohol
-ynol
name of alkyne that is a substituent
alkynyl (ex. ethynyl)
molecule that contains both double and triple bonds
alkenyne
how to number alkenyne
starting end closest to the functional group that appears first
simplest form of alkyne
acetylene (ethyne)
consist of closed ring of carbon atoms containing one or more triple bonds
cycloalkyne
the linear nature of alkyne unit makes cycloalkynes __
strained
because of linear nature of alkynes, cycloalkynes are __ __ occuring organic compounds
very rare
General Formula of cycloalkynes
CnH2n-4
Two types of alkynes
- terminal
- internal
a carbon-carbon triple bond at the end of the carbon chain
terminal alkynes
carbon-carbon triple bond in the middle of the carbon chain
internal alkynes
boiling point of alkynes compared to other hydrocarbons
higher boiling point
electric field of alkynes
more susceptible to distortion
why is the electric field of alkynes more susceptible to distorition
due to increased number of weakly held electrons
boiling points of alkynes rise in proportion to the
size of molecular structres
boiling points of alkynes rise with the increase of
molar mass
density of alkynes
- lighter, lower density than water
- become more dense as mass increases
physical state of alkynes
- odorless, colorless
- first three alkynes are gases
- next eight alkynes are liquid
- all alkynes higher than there are solids
physical state:
2-4 carbon alkynes
gases
physical state:
5-12 carbon alkynes
liquid
physical state:
13 and above carbon alkynes
solid
solubility of alkynes
- dissolve in organic solvents
- slight solubility in polar solvents
- insoluble in water
example of non polar organic solvents
- benzene
- ether
polarity of alkynes
- nonpolar
- more electronegative than alkenes and alkanes
why are alkynes more electronegative than alkanes and alkenes
due to sp hybridized carbon atom
Alkynes: addition reactions
addition across triple bond to form alkanes
Different addition reactions of alkynes
- hydrogenation
- halogenation
- hydrohalogenation
- hydration
- oxidation
- polymerization
- an addition reaction where hydrogen molecules are used to saturate organic compounds
- process is effective under certain catalytic conditions and controlled temperatures depending on the type of hydrocarbon
- undergo the same with the same catalysts used in alkene
hydrogenation
- involves the reaction of a compound with a halogen and results in the halogen being added to the compound
- possible to stop this reaction at alkene stage by runnint it at temperature slightly below 0C
halogenation
- When hydrogen halide is treated with alkynes (triple bond compounds) it results in the formation of gem halides.
- Gem halides are the compounds in which two halogens are attached to the same carbon atoms in a molecule.
hydrohalogenation
compounds in which two halogens are attached to the same carbon atoms in a molecule
Gem halides
- addition of water to alkynes
- formes aldehydes and ketones
hydration
what is formed after hydration of alkynes
- aldehydes
- ketones
hydration in alkynes
water across triple bond via carbocation mechanism
loss of electrons during a reaction by a molecule, atom or ion
Oxidation
Alkynes undergo ozonolysis to give
- acid anhydrides or diketonesion
- carboxylic acid
alkynes can be polymerized by both
- cationic methods
- free-radical methods
because of the linear shape of alkynes, __ __ does not occur
geometric isomerism
- due to the different arrangment of carbon atoms in the chain that is straight-chain or branched
chain isomerism
- due to the difference in the location of triple bond
position isomerism
- alkynes are isomeric with alkadienes both being represneted by the general formula CnH2n-2
functional isomerism