6 Organic Analysis Flashcards
(14 cards)
high resolution mass spec
very sensitive so allows masses to be given to 4 or 5 d.p. . This is useful for compounds with the same Mr such as CH3CH2CH3 and CH3CHO
test for primary or secondary alcohols
use acidified potassium dichromate
goes from orange to green
test for aldehydes
Tollen’s Reagent - silver mirror formed
Fehling’s solution - brick red ppt formed from blue
test for alkenes
add bromine water
goes from orange to colourless
test for carboxylic acid
add sodium carbonate
produces CO2, which turns limewater cloudy
test for halolakanes
add NaOH and warm. Acidify using HNO3 and add AgNO3.
forms coloured precipitate of AgX
Mass spectrometry using time of flight
gives the Mr of the comounds
Why is electron impact a bad method to use with organic samples?
the sample can be fragmented, causing other, incorrect, peaks
how does infrared spectroscopy work?
bonds in the molecule absorb infrared radiation at characteristic wavelengths. The spectrometer measures the percent of infrared transmitted and produces a graph.
fingerprint region
area below 1500cm-1
unique for every compound and can be distinguished using known spectra from a data base
C=O infrared spectra
strong, sharp peak at 1680-1750 cm-1
O-H in alcohols infrared spectra
wide peak at 3230-3550 cm-1
wider due to hydrogen bonding
O-H in acids infrared spectra
very wide peak at 2500–3000 cm-1 due to delocalisation in the -COOH and hydrogen bonding
why does increase emissions of CH4, CO2, H2O etc cause an enhanced greenhouse effect?
they absorb infrared radiation in their bonds, retaining more heat, enhancing the greenhouse effect
