alkenes Flashcards
what are alkenes?
hydrocarbons with at least C-C DOUBLE bond
does methene exist? why not?
no, because methene only has 1 C atom, so it cannot have a C-C double bond
how do you draw displayed formula for alkenes?
make sure each carbon has 4 bonds, no more, no less
describe the physical properties of alkenes
same as alkanes; covalent discrete
- low mpt
- insulator
- soluble in oils
do alkanes or alkenes have higher melting points?
alkanes, because there are more atoms in each molecule
describe the chemical properties of alkenes
alkenes contain double bonds, one of them is weaker so it breaks easily
this one can break and leave the other in place, making them very reactive
are alkenes saturated or unsaturated?
unsaturated, they contain double C-C bonds
MORE REACTIVE THAN ALKANES
what types of reactions do alkenes undergo?
addition reactions only
what does the addition of C2H4 and X2 make?
C2H4X2 - easy!
how do addition reactions work?
double bond breaks, one Br atom joins on either side of where the double bond was
what are the differences between addition and substitution?
- only one product with addition of halogens
- no additional energy is required for addition
- addition forms a dihalo product, substitution forms a monohalo product
addition can also occur with
- hydrogen halide
- water
when an alkene and water reacts, what is the product?
an alcohol
but-2-ene + water
butan-2-ol
what is the test to see if you have an alkENE or alkANE
- react it with Br2 (aq) - bromine solution/bromine water, do not use UV light
if it is an alkane, there will be no colour change
if it is an alkene, it will turn colorless
