chem11: unit 10 (cyclic hydrocarbons, alkyl groups, aromatic hydrocarbons)

how many carbon atoms can cyclic compounds have in a ring?

3, 4, 5, or more

corners of the shape of cyclic compounds...

represent the carbons (atoms are known to be present but not drawn)

when naming cyclic compounds...

-follow the same rules as regular alkane, alkene, and alkyne

-indicate that the hydrocarbon is cyclic by adding the prefix "cyclo-"

when is numbering needed for cyclic alkenes and alkynes?

when there is more than one double or triple bond

how to number cyclic alkanes

1) pick one double/triple bond and number it as 1

2) number the other ones according to this number to obtain a lowest set of overall values

*the first double/triple bond must be located between carbon #1 and #2

cyclopentane

5 single bonded carbons in a ring

1, 4 cyclohexadiene

6 carbons with two double bonds at position 1 and 4 in a ring

cyclobutyne

4 carbons in a ring with one triple bond

substituent

a group/an element that can be added to the main parent carbon chain in place of a hydrogen atom

alkyl groups

an alkane which has lost one hydrogen atom

what letter usually represents an alkyl group?

"R" (means radical; incomplete)

how is the name of an alkyl group similar to its parent alkane?

the "-ane" is replaced by "-yl"

the longest chain of C atoms...

gives the parent name of the molecule

the side chain (substituted alkyl groups)...

are names using the root and the suffix "-yl"

why are the C atoms of parent chains numbered?

so that side chain(s) are attached to the lowest possible numbers

what do you do when there is more than one identical alkyl group presented?

indicate the amount by adding a prefix such as di-, tri-, etc. (note: the prefix will not be taken into consideration when alphabetizing the alkyl groups

when is numbering needed for cyclic hydrocarbons?

when there is more than one alkyl group

how to number cyclic hydrocarbons

1) pick one of the alkyl groups and number it as 1

2) number the other groups according to this number to obtain a lowest set of overall values

how does a double or triple bond impact chain/cyclic alkene or alkyne numbering?

the double or triple bond has a higher priority towards numbering

things to consider when naming alkyl groups

-the position of the side chain

-a dash

-the name of the alkyl group

-the name of the parent, separated with a comma

methyl propane

1 carbon alkyl group similar + 3 single bonded carbons parent chain

2, 3 - dimethyl propene

1 carbon and 2 carbons alkyl group similar + 6 carbons with a double bond

how to list alkyl groups

alphabetical order (i.e. 4-ethyl, 5-methyl, 1-hexene)

how else can alkyl groups be named?

by how they are arranged

aromatic hydrocarbons

-made up of units of benzene

-have a basic structure of 1 or more rings of 6 carbon atoms with 3 alternating double bonds on each ring

why is bonding unusual for aromatic hydrocarbons?

all C-C bonds are the same length and strength (recall: resonance)

why are compounds with a benzene group called aromatic hydrocarbons?

they have distinct aromas/odours

when is a benzene named as "phenyl"?

when it acts as a substituent

what to do when naming a di-substituted aromatic group

the prefix "ortho-", "meta-", and "para-" are used