Organic Chemistry 2 - Exam 2

carbonyl

C=O

alkyl group

carbon and hydrogen group

ketone

2 alkyl groups bonded to the carbonyl carbon atom

aldehyde

1 alkyl group and 1 hydrogen group bonded to the carbonyl carbon atom

electrophile

electron deficient, searches for and accepts electron pairs

nucleophile

electron rich, donates electron pair

ketone naming

replace normal -e at the end with -one

number the longest chain with carbonyl with numbering as low as possible for carbonyl

cyclic ketones have carbonyl assigned as #1

naming aldehydes

replace final -e with -al

aldehydes are at the ends on chains so it is #1 for substituents

if it is a substituent of a large unit like a ring, carbaldehyde

carbaldehyde

used when an aldehyde group is a substituent of a large unit like a ring

how to name if ketones or aldehydes are a substituent with a higher priority functional group at the root

prefix oxo- if long chain

not in chain is formyl-

carbon right next to carbonyl carbon

alpha

boiling point of ketones and aldehydes

larger than normal ethers or alkanes, lower than alcohols

cant H-bond but can accept H bonds

good solvents

grignard reagent

R-MgX

used to make alcohols

NaOCl

bleach

oxidizes secondary alcohols into ketones

ether

R-O-R’

HOAc

acetic acid, proton source to help with making ketones from secondary alcohols

synthesizing aldehydes to ketones

synthesizing primary alcohols to aldehydes

use NaOCl and TEMPO catayst

ozonolysis of alkenes

uses alkenes to make ketones and aldehydes

uses ozone at low temps, and a mild reduction agent (CH3)2S

phenyl ketones and aldehydes - friedal crafts acylation

uses AlCl3 and H2O

another reaction for phenyl ketones and aldehydes - gatterman koch

uses CO and HCl, then AlCl3 or CuCl

alkyne hydration to make ketones and aldehydes - acid and merciric salts

uses Hg2+, H2SO4, and water

alkyne hydration with hydroborationi oxidation to make aldehydes

uses di-borane, H2O2, and NaOH

anti mark

synthesis of ketones from carboxylic acids

uses LiOH, R-Li and H3O+

synthesis of ketones and aldehydes from nitriles

nitrile - C triple bond N

uses grignard reagent with H+ and H3O+

DIBAL-H

used to reduce nitriles

Reacting nitriles with DIBAL-H to make aldehyde

uses DIBAL-H and H3O+

acid chlorides to aldehydes

uses Li+-AIH(O-t-Bu)3 and H20

acid chlorides to ketones

uses R2CuLi

benzene

C6H6

alternating pi bonds rapidly intercoverting - resonance hybrid

has 3 conjugated pi bonds (double bond separated by a single bond)

sp2 hybridized and trigonal planar

where is electron density in benzene ring

above and below the plane with P orbital overlap

conjugated pi bonds make the benzene

less reactive than normal C=C bonds

makes it a functional group because of this special property

what do the pi electrons do for benzene

makes it electron rich due to the electron density above and below the plane to act as a nucleophile that will react with an electrophile

benzenes do not do what reaction

addition, they only do substitution

heat of hydrogenation with benzene

much more stable than expected based on trends, 3 bonds on a ring if it were not benzene would be less stable

explains the lack of reactivity in addition reactions

how many pi molecular orbitals are there

6 p-orbital combine to make 6 pi molecular orbitals

lowest energy MO

no nodes with all constructive overlap

how many bonding and non bonding MO’s in benzene

3 bonding and 3 antibonding

how many nodes in bonding MO of benzene - HOMO

1 node - region with no probability of finding an electron

splits horizontally or vertically

anti-bonding MO’s in benzene

2 nodes

more antibonding = more pi *

LUMO

highest MO in benzene

all antibonding

3 nodes

MO’s for cyclobutadiene

can be all bonding, 1 node, or 2 nodes with all antibonding to make pi*

degenerate

orbitals having the same energy

intermediate energy levels with 2 orbitals at each level

4 criteria for aromaticity

1. must be cyclic

2. the molecule (or the aromatic part) must be planar

   1. all p orbitals on carbon must be parallel so the the pi electron density can be delocalized

3. ring must be completely conjugated

   1. has a p orbital on every ring atom that overlaps with another p orbital

4. must satisfy huckels rule

huckels rule

must contain 4n+2 pi electrons

• n is an integer - 0,1,2,3,4

  • gives 2,6,10,14,18

(count double bonds and lone pairs on carbon)

antiaromatic

systems that fulfill criteria 1-3 but not huckels rule, has 4n electrons

ex. cyclobutadiene

non aromatic

neither aromatic or antiaromatic, lacking continuous ring of overlapping p orbitals required for aromaticity or antiaromaticity

what is more stable antiaromatics or non-aromatics

nonaromatics

annulenes

hydrocarbons in a single ring containing a single ring with alternating c=c and c-c bonds

for naming - indicate the number of atoms in the ring in brackets and add the word annulene

annules like [10] annulene satisfies huckels rule but it is not planar due to steric strain that pushes H’s close

some are aromatic and some are not either due to huckels rule not being fulfilled or it cannot be planar

aromatic ions

can have charges and be aromatic

lone pair must lie in the p orbital

radicals cannot be aromatic or antiaromatic, only nonaromatic - odd number of electrons

aromatic cations

can be aromatic

polyaromatic hydrocarbons PAH’s

2 or more rings with alternating double and single bonds fused together

to join 6 membered rings together

• anthracene

• penanthrene - angular

number of fused rings increases, the number of resonance forms increases

anthracene

3 linearly fused benzene rings

phenanthrene

angularly fused benzene rings

heterocyclic aromatics

rings containing O,N,S or other atoms

ex. pyridine - 1 nitrogen atom

have lone pairs so we need to know if they are localized on heteroatom or part of the delocalized pi systems

ex. pyridine has the lone pairs in the plane and there is still p orbital overlap

ex. pyrrole is a 5 membered ring that has a lone pair to make 6 pi electrons

basicity in nitrogen containing heterocycles

antiaromatics are much less basic

N-H are not basic

allotropes of carbon

different structural forms of the same chemical element in the same physical state - diamond and graphite

naming monosubstituted benzenes

use prefix of the substituent followed by benzene

phenol

toluene

aniline

anisole

styrene

acetophenone

benzaldehyde

benzoic acid

naming disubstituted benzenes

name based on prefixes or numbers

if the 2 groups are different, alphabetize the names of substituents preceding the word benzene

if

ortho, o-

adjacent carbon

meta, m-

2 carbons away

para, p-

opposite sides, 3 carbons away

xylenes

dimethylbenzenes can be o, m, or p

naming benzenes if the two groups are different

when it doesn’t have a trivial name - alphabetize the names of the substituents followed by benzene

when it has a trivial name - name it as a derivative of that parent, base is assumed to be in the 1st position

naming benzene rings with more than 2 substituents

indicate positions by numbers, numbered to give lowest possible numbers to the substituents, when they are different, list in alphabetical order

when benzene group is a substituent

called phenyl group (Ph), usually when hydrocarbon is unsaturated or when it is on a larger unit

benzyl

alternative name for the phenylmethyl group

benzene IR absorption

sp2 C-H above 3000, makes it different that the normal sp3 C-H

C=C 1600-1500 fingerprint region

benzene H NMR

7ppm for aromatic ring H

7-9 Hz for ortho

0-2.5 Hz for meta

1.5-2.5 ppm for benzylic carbon hydrogen

benzene C NMR

sp2 C is 120-150 ppm, very broad

H NMR diagnostic patterns for monosubstituted benzenes

ortho - 2 - doublet

mata -2 - triplet or doublet of doublet

para 1

H NMR patterns for disubstituted benzenes with different substitients

ortho - one big coupling of doublet with split peaks

meta - no big coupling with 1 signal, another one has 2

para - symmetrical with 2 H doublets

anything symmetrical will have 1 signal because they are all equivalent