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Transcript
An Introduction to Organic
Compounds
Nomenclature, Physical Properties, and
Representation of Structure
1
Contents of Chapter 2

Nomenclature

Structures of Alkyl Halides, Alcohols,
Ethers, and Amines

Physical Properties

Conformations of Alkanes

Cycloalkanes
2
Counting to Ten in Organic










01 = meth
02 = eth
03 = prop
04 = but
05 = pent
06 = hex
07 = hept
08 = oct
09 = non
10 = dec
Mother
Enjoys
Peanut
BUTter
PENTagon
HEXagon or HEX nut
HEPTember (Roman sept is Greek hept)
OCTober
NONember (Roman nov is Greek non)
DECember
3
Alkanes
4
Primary, Secondary, Tertiary





A primary carbon has one other C directly bonded to it.
A secondary carbon is directly bonded to two other C’s.
A tertiary carbon is directly bonded to three other C’s.
Multivalent atoms are 1º, 2º, or 3º by bonding to C’s.
Univalent atom or group not really 1º, 2º, or 3º on its
own - ID depends on type of carbon it is bonded to.
5
Nomenclature of Alkyl
Substituents

There are four alkyl groups that contain
four carbons
6
Nomenclature of Alkyl
Substituents

The prefix sec- occurs only in sec-butyl
7
Nomenclature of Alkyl
Substituents

The prefix tert- can be used with butyl or
pentyl (also known as amyl) but not with
hexyl
8
IUPAC Systematic
Nomenclature - Alkanes
1. Determine longest continuous chain (i.e.
parent hydrocarbon)
2. Cite the name of substituent before the
name of the parent hydrocarbon along
with the number of the carbon to which it
is attached
9
IUPAC Systematic
Nomenclature - Alkanes
3. Number in the direction that gives the
lower number for the lowest-numbered
substituent. Substituents are listed in
alphabetical order – neglecting
prefixes such as di- tri- tert- etc.
10
IUPAC Systematic
Nomenclature - Alkanes
4. When both directions
yield the same lower
number for the
lowest numbered
substituent, select
the direction that
yields the lower
number for the next
lowest numbered
substituent
11
IUPAC Systematic
Nomenclature - Alkanes
5. If same substituent numbers are
obtained in either direction, number in
direction giving lowest number to the
first named substituent
12
IUPAC Systematic
Nomenclature - Alkanes
6. If compound has two or more chains of
the same length, parent hydrocarbon is
chain with greatest number of
substituents
13
IUPAC Systematic
Nomenclature - Alkanes
7.
Names such as sec-butyl and tert-butyl are
acceptable, but systematic substituent names are
preferable
Numbering of the substituent begins with the carbon
attached to the parent hydrocarbon
This number together with the substituent name is
placed inside parentheses
14
Nomenclature of Cycloalkanes

Cycloalkanes generally are shown as skeletal
structures
15
Nomenclature of Cycloalkanes
1. Ring is the parent hydrocarbon unless the
alkyl substituent has more carbons; in that
case the substituent becomes the parent
hydrocarbon
If only one substituent, no need to give it a
number
16
Nomenclature of Cycloalkanes
2. If the ring has 2 substituents, list in
alphabetical order and give number 1 to
first named group
17
Nomenclature of Cycloalkanes
3. If there is more than one substituent, list in
alphabetical order; one substituent is given
the position number 1; number either
clockwise or counterclockwise - lowest
numbers
18
Nomenclature of Alkyl Halides

Common name - Name the alkyl group
first, followed by the name of the
halogen expressed as an -ide name
19
Nomenclature of Alkyl Halides

IUPAC name - The halogen is treated
as a substituent
20
Nomenclature of Ethers

Common name Name(s) of alkyl
group(s) listed
first followed by
the word “ether”
21
Nomenclature of Ethers

IUPAC name - The smaller alkyl group
is converted to an “alkoxy” name and
used as a substituent
22
Nomenclature of Alcohols

Common name Name of the Alkyl
group followed by
the word “alcohol”
23
Nomenclature of Alcohols


IUPAC name - The OH group is a site of
reactivity (a functional group)
Functional group is denoted by the suffix, “ol”
CH3OH
CH3CH2OH
methanol
ethanol
24
IUPAC Nomenclature of
Alcohols
1. Parent Hydrocarbon is the longest
continuous chain that contains the OH
2. Number the chain in direction that gives
functional group the lowest number
3. If both a substituent and a functional
group are present, the functional group
gets the lower number
25
IUPAC Nomenclature of
Alcohols
4. If the functional group gets the same
number when counted from both
directions, use direction which gives the
substituent the lower number
5. If there is more than one substituent, cite
substituents in alphabetical order
26
IUPAC Nomenclature of
Alcohols

System is summarized as [Substituent]
[Parent Hydrocarbon] [Functional Group]
27
Nomenclature of Amines


Common name - Name of the Alkyl group(s)
(in alphabetical order) followed by the
syllable “amine”
The whole name is a single word
CH3NH2
methylamine
CH3NCH2CH2CH3
methylpropylamine
28
Nomenclature of Amines



IUPAC name - The NH2 group is a site of
reactivity (a functional group)
Functional group is denoted by the suffix,
“amine”
Final “e” of longest alkane group replaced by
suffix “amine”
CH3CH2CH2CH2NH2
1-butanamine
butan-1-amine
29
IUPAC Nomenclature of
Amines
1. Find the longest chain bonded to the
nitrogen
Final “e” is replaced with “amine”
2. Number the carbon to which nitrogen is
bonded
3. Number any substituents on the alkyl
chain
4. Use italicized N- for each additional
substituent(s) on the nitrogen
30
Properties of Alkyl Halides,
Alcohols, Ethers, & Amines


For alkanes, there are only induced
dipole-induced dipole interactions (also
known as van der Waals forces or
London forces)
van der Waals forces are a function of
surface area
31
Induced Dipole-Induced
Dipole Interactions
32
Hydrogen Bonding: Strong
Dipole-Dipole Interactions
33
Dipole-dipole Interactions


Particularly important for ethers vs. alkanes
Ethers and alkyl halides have dipole moments,
but their intermolecular attractions are not as
strong as hydrogen bonds
34
Comparative Boiling Points
35
Solubility

The more carbons that are present, the
less soluble an organic compound is in
water
36
Newman Projections


A convenient way to describe
conformation isomers is to look at the
molecule along the axis of the bond of
interest
A Newman projection is a graphical
representation of such a view
37
Conformations of Alkanes:
Rotation About C-C Single Bonds
38
Chair Conformation of
Cyclohexane
39
Drawing Cyclohexane in the
Chair Conformation
40
Interconversion of Cyclohexane
Conformations


As a result of simultaneous rotation about
all C-C bonds, a chair conformation of
cyclohexane can interconvert to another
chair conformation by a ring-flip
In the process, equatorial bonds become
axial and vice versa
41
Monosubstituted
Cyclohexanes

When there is one substituent on the
cyclohexane ring, the two chair
conformations are no longer equivalent
42
Conformations of 1,4Disubstituted Cyclohexanes
two methyl groups
on same side of ring
two methyl groups on
opposite sides of ring
H
CH3
H
CH3
cis-1,4-dimethylcyclohexane
H
CH3
H3C
H
trans-1,4-dimethylcyclohexane
43
Conformations of 1,4Disubstituted Cyclohexanes
The cis isomer must have one
substituent in an axial position and one
in an equatorial position

H
H
ring-flip
CH3
H
CH3
H3C
equatorial
axial
H
CH3
axial
cis-1,4-dimethylcyclohexane
44
Conformations of 1,4Disubstituted Cyclohexanes

The trans isomer has both substituents
in either the equatorial or in the axial
positions
axial
CH3
H
ring-flip
CH3
H3C
H
H
equatorial
equatorial
H
much more stable
much less stable
trans-1,4-dimethylcyclohexane
CH3
axial
45
Conformations of cis-1,3Disubstituted Cyclohexanes

A cis-1,3-disubstituted cyclohexane can
exist in one of two conformations
H
ring-flip
H
CH3
H3C
C
CH3
CH3
H
H3C
H
C
CH3
CH3
CH3
much more stable
much less stable
cis-1-tert-butyl-3-methylcyclohexane
46
Conformations of trans-1,3Disubstituted Cyclohexanes

Both conformers of trans-1-tert-butyl-3methylcyclohexane have one substituent
in an axial position and one in an
equatorial position
47