Organic Chem Flashcards
Dehydration of alcohol; mechanism?
Alkene; E1 or E2
Bond dissociation energies b/t 2 elements depend on…
hybridization
sp3-sp3 < sp3-sp2 < sp3-sp
Which hybridization has the highest bond dissociation energy?
sp (forms strongest bond ∴ releases the most energy when broken)
smaller atoms form stronger/weaker bonds?
smaller atoms form shorter bonds → shorter bonds are stronger bonds
∴ smaller atoms form stronger bonds
what type of alkene has the weakest bond? Why?
unsubstituted alkene (all H) - more substituted alkenes are more stable
What is characteristics of stronger bonds?
- smaller substituents
- more EN substituents
What is unique about the amide C=O and C-N bond?
Can act as both SB and DB
- shorter than normal C-N
- longer than normal C=O
If amides were protonated, where would the proton go?
O
- most basic site
- resonance causes it to have partial neg charge
Hybridization of amide C and N
sp2 (due to DB formed on some resonance structures)
VSPER of amide
6 atoms are all coplanar (trig planar around C & trig planar around N)
EDG makes things more basic/acidic?
Basic
For something to be absorbed through respiration, it must be…
- gas
- liquid with low BP (high vapour pressure)
- NO H-BONDING
What force (e.g. VDW, dipole, H-bond…) is experienced with interactions between 2 hydrophobic tails?
VDW
Rate sp, sp2, sp3 in terms of acidity
sp > sp2 > sp3
rate sp, sp2, sp3 in terms of basicity. Explain.
sp3 > sp2 > sp
DB draw electron density from the EN element
Which element tends to be the most basic?
N
Amines are very good…
nucleophiles
pKa + pKb =
14
aromatic amine
N must be in the aromatic ring
degrees of unsaturation:
N
Halogens
O
Pretend each is H and change number according to…
N = +1
Halogens = -1
O = 0
for IR, ↑cm-1 = __ energy. What does this mean?
↑
C=O is 1700
C-O is 1300
C=O bond has ↑energy ∴ stronger than C-O
Conjugation
alternating DB and SB
What is found around 1630 - 1600 cm-1?
Amide
what is the wavelength of ester, ketone, aldehyde?
ester: 1735
aldehyde: 1725
ketone: 1710
Stronger covalent bond = ____ H-bond
weaker
Weaker bonds show up as a broad/narrow peak in IR?
broad
NMR: upfield = ?, downfield = ?
upfield: shielded (0)
downfield: deshielded (10)
NMR for benzene
singlet at 7.0 ppm
NMR value: carbox acid
10-12 (broad)
NMR value: aldehyde
9-10
NMR value: aromatic H
7-8
NMR value: vinylic H
5-6
NMR value: alkoxy H
3.5-4
NMR value: alpha-H
2-2.5
NMR value: para-substituted ring
7.0 (dd)
which ring substitution has the least amount of peaks for NMR?
para
C-NMR: substitution vs. ppm
tertiary = lowest ppm (right)
primary = highest ppm (left)
3 > 2 > 1
Ester + NaOH
Ester is hydrolyzed to form
- carboxylate
- alkoxide
(Ester will dissolve in NaOH if refluxed)
Diols are axial-equatorial / axial-axial / equatorial-equatorial?
axial-axial / equatorial-equatorial both works, but cannot be axial-equatorial
H-bonding in diol occurs…
between O of one OH and H of other OH
dipolar
have dipole moment
optical isomer
rotate light in diff directions
geometrical isomer
differences in DB or ring structure
enantiomer
Non-superimposable mirror images
SR RS
Diastereomer
Non-superimposable non-mirror images
SR RR or SS
configurational isomer
identical bonds with different spatial arrangement of atoms
(+) polarity = CW or CCW?
(-) = ?
CW;
CCW
does having a chiral center mean the compound is optically active?
no, meso compounds have symmetrical, opposite chiral centers that cancel out any rotation
max number of stereoismers
2^n (n = number of chiral centers)
epimer
Deals with carbohydrates/sugars
- chirality changes at only 1 C
Anomer
special type of epimer where only difference in chirality is at anomeric C. Straight chain form would be identical.
e.g. a-D-glucose vs. B-D-glucose
Anomeric C
C in sugar that is bound to 2 oxygens
protic solvents hinder ____
nuc that can H-bond
What stereochemistry does SN2 prefer?
less hindered
reaction kinetics of SN2
second order
k[nuc][elec]
preferred solvent for SN2
polar, aprotic
e.g. ethers, ketones
A racemic mixture forms if SN_ reaction occurs and the reactant was ____
1;
chiral
how to distinguish between substitution and elimination?
elimination usually requires higher temperature
physical properties of stereoisomers
enantiomers: identical physical properties
diastereomers: different physical properties
physical property of racemic mixtures vs pure enantiomers
racemic mixtures are generally more stable
- higher MP if solid
- higher density
which reaction happens faster: chlorination or bromination of alkane?
chlorination
what happens to product formation when energy is added into a system?
less stable compounds form to absorb excess energy
how to find number of structural isomers?
= number of unique C on alkane
E2 conditions
- basic
- high temperature
E1 conditions
- acidic
- high temperature
regioselectivity deals with…
Markovnikov’s rule
The first substituent to be attached goes onto least substituted C
(e.g. Br would end up on more substituted C)
Stereoselectivity deals with…
Syn vs Anti
Substituents likes to add to the least hindered face
1,2 addition to conjugated diene is under ___ control
kinetic (product depends on most stable INTERMEDIATE)
1,4 addition to conjugated diene is under ___ control
thermodynamic (product depends on most stable PRODUCT)
- higher temperature allows less stable intermediate to form
- rearrangement occurs to form more stable product
is the transition state of Diels-Alder reaction aromatic?
yes
the dienophile of a Diels-Alder reaction should have EWG/EDG attached to it to help the reaction proceed?
EWG
conditions for fastest Diels-Alder reaction
- EDG on diene
- EWG on dienophile
- Less bulky
pericyclic reactions
repositioning pi & sigma bonds through formation of cyclic intermediate
base unit of terpenes
isoprene (5C)
monoterpene has __ C
10C
which lab technique is used to separate terpenes?
steam distillation
process of steam distillation
- pulp boiled
- oil from pulp is distilled
- distillate = water + terpenes
- separate using extraction techniques
UV spectroscopy deals with…
pi bonds & conjugation
effect of branching on BP
more branched = decrease BP
alkoxide
good base?
good nuc?
C-O(-);
good base;
bad nuc
are ketones & aldehydes protic or aprotic solvents?
aprotic
is UV spectroscopy the same for aldehydes & ketones?
no, their pi-bonds are different
ketals & acetals are formed/removed under ____ conditions
acidic
hemiketals & hemiacetals are formed under ___ conditions, and removed under ____ condition
basic;
any
is carbox acid a strong or weak acid?
weak
saponification
ester -> carboxylate (R removed from OR -> O-)
in the presence of xs. H2O and KOH
transesterification
exchange OR group on ester
acid anhydride synthesis from carb axid is a ___ reaction
dehydration (add heat)
are amides found in AA?
no, they are found in peptide chains! (peptide bond)
relative reactivity:
acid halide, amine, ester, anhydride
acid halide > anhydride > ester > amine
each new C-O bond increases oxidation state by ___
+2
each new C-O bond increases oxidation level by ____
+1
Grignard reactions always have __ in the product
OH (alcohol)
when does grignard add twice?
when there is a LG on the C=O
is grignard a base/acid (strength?)?
what type of solvent does it prefer?
strong base
polar aprotic solvent (Et2O)
workup of grignard reactions use…
weak acid
what is removed during aldol condensation?
H2O (O comes from C=O of a second aldehyde or ketone, H2 comes from CH3 on R group of first aldehyde/ketone)
reactant and product of Claisen Condensation Reaction
R: ester + ester
P: B-ketoester
biological application of aldol condensation
4th step of glycolysis (retro-aldol reaction)
biological application of Claisen condensation
fatty acid synthesis
transesterification is driven forward by…
Le Chateliers
biological application of transesterification
fatty acid -> TG breakdown (saponification)
iodoform test is used for…
methyl ketones
methods in which aldehyde/ketone -> alkane
1) Clemmensen: Zn(Hg)/HCl [acidic]
2) Wolff-Kishner: NH2NH2 [basic]
3) SHCH2CH2SH + Raney Nickel [neutral]
most transition metals have __ oxidation states. This means that they are good ____ agents
\+; reducing agents (go from 0 to some positive number = oxidized)
Wolff-Kishner reaction is driven forward by…
removing N2
protecting groups for:
1) aldehyde
2) ketone
2) alcohol
1) acetal
2) ketal
3) silyl ether
match up:
anabolism, catabolism, reduction, oxidation
anabolism = reduction catabolism = oxidation
anabolism usually takes places in the ___ while catabolism takes place in the ___
cytosol;
mitochondria (except glycolysis)
NADH is responsible for…
reduction of aldehydes & ketones
FADH2 is responsible for…
hydrogenation of pi-bonds
I2/OH is used to test for…
Colour change?
methyl ketones
yellow ppt
K2CrO4/H2SO4 is used to test for…
Colour change?
primary & secondary alcohols
aldehydes
(orange -> green)
Br2/CCl4 is used to test for…
Colour change?
alkenes
brown -> clear
IBr/CCl4 is used to test for…
Colour change?
unsaturated fats
purple -> clear
derivative for aldehydes & ketones
2,4-dinitrophenylhydrazone
derivative for alcohols
benzylesters
derivative for osazones
sugars
In mass spec, Cl has what ratio?
3:1
in mass spec, Br has what ratio?
1:1
Parent peak in mass spec
Peak of highest mass (furthest right on the y-axis)
Base peak in mass spec
tallest peak in the whole graph (denoted as 100 for relative intensity; most intense)
mutarotation
flip-flop between a and B forms of ring (straight chain form is intermediate)
aldose ketose conversion occurs via ___ intermediate when acid catalyzed
enediol
aldose ketose conversion occurs via ___ intermediate when base catalyzed
enolate
glycosidic linkage is formed by a ___ reaction
hydrolysis
which polysaccharides branch?
amylopectin & glycogen
which polysaccharides are linear?
amylose & cellulose
what type of interactions are found between cellulose molecules?
H-bonding
____ linkages are usually responsible for branching in polysaccharides
1,6
Nitric acid oxidizes glucose to…
Optically active?
glucaric acid;
Yes
oxidized mannose =
Optically active?
mannaric acid;
yes
oxidized galactose =
Optically active?
galactaric acid;
No (the COOH on both ends makes it meso compound)
oxidized allose =
Optically active?
allaric acid;
No (the COOH on both ends makes it a meso compound)
Benedict’s Test (Fehling’s solution)
Test for reducing sugars (e.g. aldehydes) vs. non-reducing sugars (e.g. ketones)
+ test: blue -> red (there is a reducing sugar present)
Tollen’s Test
Test for aldehydes (distinguish between aldehyde & ketones)
+ test: silver mirror forms (when aldehyde present)
Periodate oxidation
cleaves C-C bonds in sugar (will end up with a bunch of 1 C fragments)
- terminal C gains 1 bond to O
- internal C gain 2 bonds to O
Killiani-Fischer synthesis
increase C chain of aldose by 1 (cyano group added)
Ruff degradation
Remove 1 C from aldose (decarboxylation)
Wohl Degradation
remove 1 C from aldose (lots of N intermediates)
how to increase the length of aldose?
Killiani-Fischer synthesis
How to decrease the length of aldose?
Ruff degradation & Wohl degradation
what is the only oxidation step in glycolysis?
G3P -> 1,3 BPG
