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<\/a>1. Condensed Formulae<\/strong><\/h2>\nA somewhat intermediate place within these formulae is what we call the “condensed formula<\/strong>“. It’s a way of depicting molecules completely in text form. In the days before word processors and graphics programs made it a cinch to include pictures, condensed formulae were the method of choice when you wanted to convey the structure of something without actually having to draw it.<\/p>\n![\"four-ways-of-depicting-propane-lewis-structure-structural-formula-line-diagram-skeletal-formula-condensed-formula\"](\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/11\/1-four-ways-of-depicting-propane-lewis-structure-structural-formula-line-diagram-skeletal-formula-condensed-formula.gif\")
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It’s easy for simple hydrocarbons like propane: CH3<\/sub>CH2<\/sub>CH3<\/sub>. It’s pretty much impossible to draw a useful condensed formula for something like morphine.<\/a><\/p>\nIn between those two extremes, there are a few tricky things to keep track of. Brackets are one of them.<\/strong><\/p>\n<\/a>2. What’s The Purpose Of Using Brackets?<\/strong><\/h2>\nBrackets help in two ways. They can 1) reduce the amount of work, and 2) remove ambiguity from a structure.<\/p>\n
1) Saving Time<\/strong><\/p>\nFor example, consider the difference between writing<\/p>\n
CH3<\/sub>CH2<\/sub>CH2<\/sub>CH2<\/sub>CH2<\/sub>CH2<\/sub>CH2<\/sub>CH3<\/sub> and CH3<\/sub>(CH2<\/sub>)6<\/sub>CH3<\/sub>.<\/p>\nMuch less work, right? Chemists gravitate towards solutions that involve doing less work<\/a>. Using brackets is a no brainer.<\/p>\n2) Reducing Ambiguity<\/strong><\/p>\nA second use of brackets is to reduce ambiguity<\/strong>.<\/p>\nThink back to math: there’s a difference between 4 + 2 * 3 and (4+2)*3. In organic chemistry, we use brackets in exactly the same way.<\/strong><\/p>\nConsider a case where you have four CH3<\/sub> groups attached to a carbon. You wouldn’t write it CH3<\/sub>CH3<\/sub>CH3<\/sub>CH3<\/sub>C\u00a0 ;\u00a0 writing it like that implies a chain, and each of those CH3<\/sub> groups can only be attached to one thing. C CH3<\/sub> 4<\/sub> is a little better but having those numbers next to each other is confusing (it looks like CCH34<\/sub>). So put the CH3<\/sub> groups in brackets and write C(CH3<\/sub>)4<\/sub>. This has no ambiguity<\/strong>. An equivalent (but less efficient) way to write the structure would be CH3<\/sub>C(CH3<\/sub>)3<\/sub>.<\/p>\n3) Carbonyls<\/strong><\/p>\nCarbonyl oxygens (that’s C=O) can also be dealt with by putting them in brackets. So CH3<\/sub>C(O)CH3<\/sub> implies that the second carbon is double-bonded to an oxygen.<\/p>\n4) Branching<\/strong><\/p>\nBrackets can also be used to show branching. For example CH3<\/sub>CH(CH3<\/sub>)CH2<\/sub>CH3<\/sub> depicts a 4-carbon chain where the CH3<\/sub> in brackets is directly attached to the carbon before it. That helps to highlight a useful rule of thumb: look to the left of the bracket<\/strong> to see which atom it’s attached to.\u00a0<\/strong><\/p>\n<\/a>3. Some Additional Tricks To Know<\/strong><\/h2>\nThere are some additional tricks with structural formulas that don’t involve brackets but are still important to know.<\/p>\n
Aldehydes<\/strong> are represented by CHO<\/p>\nCarboxylic acids <\/strong>are represented by CO2<\/sub>H (or COOH)<\/p>\nEsters<\/strong> are represented by CO2<\/sub>R\u00a0 (or COOR)<\/p>\n<\/a>4. Some Representative Examples<\/h2>\nHere’s a table with some representative examples. As more come up, I’ll add them. Let me know if I’ve missed anything important!<\/p>\n
![\"translating-bracketed-condensed-formulae-into-structures-examples\"](\"https:\/\/www.masterorganicchemistry.com\/wp-content\/uploads\/2019\/11\/2-translating-bracketed-condensed-formulae-into-structures-examples.gif\")
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<\/a>5. Quiz Yourself!<\/h2>\n
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It’s easy for simple hydrocarbons like propane: CH3<\/sub>CH2<\/sub>CH3<\/sub>. It’s pretty much impossible to draw a useful condensed formula for something like morphine.<\/a><\/p>\n In between those two extremes, there are a few tricky things to keep track of. Brackets are one of them.<\/strong><\/p>\n Brackets help in two ways. They can 1) reduce the amount of work, and 2) remove ambiguity from a structure.<\/p>\n 1) Saving Time<\/strong><\/p>\n For example, consider the difference between writing<\/p>\n CH3<\/sub>CH2<\/sub>CH2<\/sub>CH2<\/sub>CH2<\/sub>CH2<\/sub>CH2<\/sub>CH3<\/sub> and CH3<\/sub>(CH2<\/sub>)6<\/sub>CH3<\/sub>.<\/p>\n Much less work, right? Chemists gravitate towards solutions that involve doing less work<\/a>. Using brackets is a no brainer.<\/p>\n 2) Reducing Ambiguity<\/strong><\/p>\n A second use of brackets is to reduce ambiguity<\/strong>.<\/p>\n Think back to math: there’s a difference between 4 + 2 * 3 and (4+2)*3. In organic chemistry, we use brackets in exactly the same way.<\/strong><\/p>\n Consider a case where you have four CH3<\/sub> groups attached to a carbon. You wouldn’t write it CH3<\/sub>CH3<\/sub>CH3<\/sub>CH3<\/sub>C\u00a0 ;\u00a0 writing it like that implies a chain, and each of those CH3<\/sub> groups can only be attached to one thing. C CH3<\/sub> 4<\/sub> is a little better but having those numbers next to each other is confusing (it looks like CCH34<\/sub>). So put the CH3<\/sub> groups in brackets and write C(CH3<\/sub>)4<\/sub>. This has no ambiguity<\/strong>. An equivalent (but less efficient) way to write the structure would be CH3<\/sub>C(CH3<\/sub>)3<\/sub>.<\/p>\n 3) Carbonyls<\/strong><\/p>\n Carbonyl oxygens (that’s C=O) can also be dealt with by putting them in brackets. So CH3<\/sub>C(O)CH3<\/sub> implies that the second carbon is double-bonded to an oxygen.<\/p>\n 4) Branching<\/strong><\/p>\n Brackets can also be used to show branching. For example CH3<\/sub>CH(CH3<\/sub>)CH2<\/sub>CH3<\/sub> depicts a 4-carbon chain where the CH3<\/sub> in brackets is directly attached to the carbon before it. That helps to highlight a useful rule of thumb: look to the left of the bracket<\/strong> to see which atom it’s attached to.\u00a0<\/strong><\/p>\n There are some additional tricks with structural formulas that don’t involve brackets but are still important to know.<\/p>\n Aldehydes<\/strong> are represented by CHO<\/p>\n Carboxylic acids <\/strong>are represented by CO2<\/sub>H (or COOH)<\/p>\n Esters<\/strong> are represented by CO2<\/sub>R\u00a0 (or COOR)<\/p>\n Here’s a table with some representative examples. As more come up, I’ll add them. Let me know if I’ve missed anything important!<\/p>\n<\/a>2. What’s The Purpose Of Using Brackets?<\/strong><\/h2>\n
<\/a>3. Some Additional Tricks To Know<\/strong><\/h2>\n
<\/a>4. Some Representative Examples<\/h2>\n
<\/p>\n<\/a>5. Quiz Yourself!<\/h2>\n