Question: Consider this carbocation:

[![enter image description here](https://i.stack.imgur.com/vPKrQ.png)](https://i.stack.imgur.com/vPKrQ.png)

We know that this carbocation would immediately rearrange - by a methyl shift - to form the more stable carbocation. 

Now, notice that the migration will produce a **chiral** center at carbon **1**. Assuming that the leaving group was a chloride, will the configuration at **1** - after the methyl shift - be retained, inverted, or racemized?

Interestingly, assuming the nucleophile is $\ce{EtOH}$, in the final product - 2-d-3-ethoxy-3-methylpentane, carbon **2** is also a chiral center. I assume that it will be racemized, as in usual SN1 reactions, but I am not sure. Am I correct?

At a very detailed level, I was also taught that in SN1 reactions, 100% racemization does **not** occur. The inverted product is slightly more than the retained product. This is because - while the leaving group is still leaving - backside attack is preferred. So, does this phenomenon also have an effect on the molecule above?

**To conclude**, I wish to know the stereochemistry at both chiral carbon **1** and **2**. Are they retained, inverted, or racemized? If racemized, then is the racemization 100%, or is the inverted product formed more than the retained one?

Answer: 
Okay so here is the situation: You have two subsitutions, methyl and 1-methylpropyl as the two substituents here. You wish to know in which order the substituents must be written in the name. You knew that substituents are arranged alphabetically, and both methyl and 1-methylpropyl start with the same letter *m*.

Consider a dictionary. It has over thousands of words that start with the letter C. But we can still arrange the words in order by looking at the second, third, fourth, fifth, *etc.* letters of the names. Similarly, if the first letters are the same, look at the second, third and fourth letters.

Here's where we arrive at the conclusion. methylpropyl will be ranked below methyl as per dictionary order. Thus the name of the compound would, in fact, be 2,2,7-trimethyl-4-(1-methyl-propyl)-nonane and the other name is not accepted.

I believe you can continue from here to name the second compound. 

**Important notes:** 

1. The inclusion of di, tri in the name must only be applied for complex subsituents such as in the case of 5-(dimethylethyl)decane. In cases such as 4-ethyl-5,5-dimethyldecane, **do not** use *d* as the starting letter. This is becase *d* is not the part of the name of the subsitituent (methyl) and only indicates how many times this subsitituent occurs in the compound.
2. Do not add hyphens between methyl and decane such as "methyl-decane". Use "methyldecane" Hyphens must only be used between numbers and subsituents for which the number represents its position in the name.
Substituents are always written in alphabetical order (without considering the numerical prefixes such as di, tri, etc). Also, in case of trimethyl and methyl propyl, having same first alphabet (i.e. m), generally the substituent with shotter name is written first. But as per my knowledge, there is no such official rule. So the name that you have suggested for the first case is acceptable. But your second name is incorrect as alphabetical order is not considered.