orgo lab quiz three

what is TLC used for

to separate miztures, check purity, identify unknowns, and monitor reactions

what is the stationary phase in TLC

silica gel

is silica gel polar or nonpolar

polar

what is the mobile phase

the solvent

what does the mobile phase do

it moves up the plate and carries compounds with it

what does the stationary phase do

it holds compounds back based on how strongly they interact with it

on polar silica, what type of compound sticks more

more polar compounds

on polar silica, what type of compound moves farther

less polar or more nonpolar compounds

on a polar silica, define low rf

compound is more polar

on polar silica, what does a high rf mean

less polar or nonpolar

how to calc rf

distance spot/distance traveled by solvent font

range of rf

between 0 and 1

on polar silica, which is more polar, rf .20 or .80

.20 bc it traveled less

which is more nonpolar on silica, .20 or .80

.80 bc it went further

what happens when the solvent is more polar

rf values usually increase bc the solvent pulls compounds farther up the plate

what happens if the solvent is less polar

rf values usually decrease bc the compounds do not move as far

what happens if the solvent is too polar

spots may travel too far and separation might be piir

what if the solvent is too nonpolar

spots may stay near the baseline and separation may be poor

best solvent system

one that gives clear, separated spots that are not all at the bottom or all at the top

how do polar silica and polar solvent work tg

polar silica holds polar compounds down while polar solvent helps move them up

with a nonpolar solvent, where does a polar compound usually go

it stays low bc it sticks to silica and solvent does no move it well

with apolar solvent, where does a polar compound usually go

it moves hgiher than before, maybe towards the middle

what happens if the initial spot is too large

it can streak or spread, making rf inaccurate

why should u mark the solvent from immediately

the solvent evaporates quickly

what happen if the solvent from reaches the top of the plate

rf vales are inaccurate

what does one spot usually suggest

one compound or a pure sample

what do multiple spots suggest

a mixture of compounds

how do you identify an unknown using tlc

compare its rf values to known stds

if two compounds have the same rd, are they the same

not def, but they might be

what does tlc tell u abt a rxn over time

whether reactants are disappearing and product is forming

how do you know a rxn is complete on tlc

there is no more reactants, only product

HDI 0

saturated compound, no rings, no db

hdi 1

1 db or 1 ring

hdi 2

2 db, 2 rings, 1 tb, or one db + ring

hdi 4

likely to have a benzene ring

if the molecule is charged, you should expect what kind of solubility

higher solubility

for the highest boiling point, what imf is favored

H bonding, so alcohols, ca’s etc. if theres an O, make it an alc and not branched

branching w bp

lowers bp

if asking for lowest bp

no H bonding and a lot of branching