Lab Exam CHEM 3460

TA’s first name

Mehdi

What does Br test for

Unsaturation

Positive Br test

immediate disappearance of the redish-brown color

What does the Lucas test test for

tertiary and secondary alcohols

Positive Lucas test

turning cloudy or forming an oily layer

Purpose of DNP test

take melting point

What does the Iodoform test test for

methyl ketones and secondary methyl alcohols

Positive Iodoform test

produces yellow precipitate

What does the Chromic Acid test test for

aldehydes, primary alcohols, and secondary alcohols

Positive Chromic Acid test

formation of a green precipitate

What does the Tollens test test for

aldehydes

Positive Tollens test

formation of a silver mirror

What is the purpose of recrystallization

to remove impurities

Characteristics of a good recrystallization solvent

dissolves impurities at all temps, but only dissolves solute at high temps

Does polar or nonpolar travel farther in TLC

Nonpolar

Does a more polar or more nonpolar solvent result in higher rf values

more polar

What gas is produced in Diels Alder lab and does it recondense

SO2 and yes

Why don’t we put a stopper on the drying tube

Some gas needs to escape so the system doesn’t explode

Why is CaCl removed from drying tubes

old CaCl is hard to get out of the drying tubes

Why are cyclic dienes more likely to dimerize

because they are locked into s-cis formation

Will a polar or nonpolar molecule travel faster through the chromatography column

nonpolar

Why don’t we let the level of solvent go below the top of the adsorbent

to avoid cracking, air bubbles, and uneven flow

What charge do EWG like

negative

What charge do EDG like

positive

Examples of EWG

NO2, CN, C=O, CA, SO3H

Examples of EDG

R groups, OR, OH, NH2, NR2, OCH3

Examples of Ortho / Para Directors

NH2, NHR, NR2, OH, OR, X, OCH3, R groups

Examples of Meta Directors

NO2, CN, CA, COOR,

Why do we use brine

to remove water from ether layer

Why are ketones more reactive than esters in a grignard reaction

the OR group in an ester makes the C=O less positive, which makes it less reactive

OH Stretch (alcohols and phenols)

3700 - 3200

OH Stretch (Carboxylic Acid)

3300 - 2500

C=O Stretch

1820 - 1630

C-H Stretch

3300 - 2700

Aldehyde C-H Stretch

2720

Carbon isotopes and ratio

12 and 13 (99:1)

Chlorine isotopes and ratio

35 and 37 (3:1)

Bromine isotopes and ratio

79 and 81 (1:1)

Nitrogen rule

If the molecular mass is an odd number, there are an odd number of nitrogens in the molecule