CHEM 51C Lecture Notes - Lecture 5: Infrared Spectroscopy, Chemical Shift, Chemical Formula

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amethystrat214

28 Jul 2016

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Document Summary

Look at molecular formula: count the carbons on the cnmr, symmetrical carbons would have the same signal. Look at hnmr for integrations, chemical shift and splitting. Compare the molecular formula to the alkane: cnhn+2: count number of carbons in molecular formula, count number of hydrogens a. If you have an o atom in the molecular formula, ignore it b. If you have a halide [f-, br-, cl-, i-], 1 halide= 1 h c. 1 ring = 1 degree of unsaturation a. ii. 1 double bond= 1 pi bond = 1 degree a. iii. 1 triple bond = 2 pi bonds= 2 degrees of unsaturation. 110-0= sp3 hybridized carbons [carbon bonding to 4 substituents] Key things to look for: multiplet in 6. 5-8 ppm- benzene ring, a doublet splitting (6 hs) , a singlet peak (9hs)= three methyl groups bonded to a carbon, singlet peak around 1-5: -oh group.

Related Questions

1.Structural isomer refers to organic compound that have the same molecular formula but different structure (bonding pattern is different). This problem is designed to guide you to explore structure isomer.

(a)Go ahead and write Lewis structure for butane (C₄H₁₀). You may draw four C atoms connect straight as like in train.

(b)In the above structure, four C atoms are connected straight in a line. If you move one C atom to the side (like 3 C atoms in a line, one connected to the middle C atom), after you supply all the H atoms to make all the C atoms saturated with 4-bonds each. Will the molecular formula for your structure drawn be different from butane?

( c) Structures you obtained in (a) and (b) are an example of structural isomers. What kind of name we can give to structure in (b) so we can differentiate it from structure in (a)?

2.Alkane is the basic building block of organic compound. We often write alkane chain as a group R. On this basic chain, we can add different functional group, like âOH for alcohol, -COOH for carboxylic acid.

(a)Methanol refers to CH₃OH. Ethanol refers to CH₃CH₂OH. Draw the Lewis structure for these two compounds.

(b) If you have a straight alkane chain, where does âOH group can be attached? How do you name it so you can know where âOH group is attached?

3. Give the Lewis structure for CH₃COOH. Give its systematic name and common name.

4. Ester refers to two alkane chains connected through a single O atom. Write the Lewis structure for this simplest kind of ester: CH₃OCH₃. Find its name and some common use.

5. Benzene molecular formula is C₆H₆. The six carbon atoms are connected to form a ring (hexagon). Draw the Lewis structure for C₆H₆. Do you think the six bond lengths between C-C atoms should be same or not according to your drawn Lewis structure?